CATin
  1. CATin
  2. CAT past papers
  3. CAT 2024 Slot 1
  4. QA

CAT 2024 Slot 1 — QA questions with answers

All 22 questions of the Quantitative Ability section (14 MCQs, 8 TITA). Try each one, then open its answer and solution.

CAT 2024 Slot 1, timed like the real exam (120 minutes, 40 a section) and scored the CAT way: +3 right, −1 for a wrong MCQ, 0 for a wrong TITA, with the full post-mock analysis. Free — sign in and you come straight back to this paper.

Sit this paper as a timed mock in CATin — free

Quantitative Ability

CAT 2024 Slot 1 · 40 minutes · +3 for a right answer, −1 for a wrong MCQ, 0 for a wrong TITA

Q47MCQPermutations & Combinations

Consider two sets A={2,3,5,7,11,13}A = \{2, 3, 5, 7, 11, 13\} and B={1,8,27}B = \{1, 8, 27\}. Let ff be a function from AA to BB such that for every element bb in BB, there is at least one element aa in AA such that f(a)=bf(a) = b. Then, the total number of such functions ff is
  1. 665
  2. 667
  3. 537
  4. 540
Answer and solution

Answer: (D) 540

Every element of BB must be hit, so count the onto functions by inclusion–exclusion. All functions: each of the 6 elements of AA can go to any of the 3 elements of BB, giving 36=7293^6 = 729. Functions missing one given element of BB map into the other 2: 26=642^6 = 64. There are 3 choices of the missed element: 3×64=1923 \times 64 = 192. Functions missing two given elements send everything to the third: 16=11^6 = 1. There are (32)=3\binom{3}{2} = 3 such pairs. Each of these constant functions was subtracted twice above but counted only once in 729, so add the 3 back. Onto functions =729−192+3=540= 729 - 192 + 3 = 540. Option C, 537, is 729−192729 - 192: it forgets to add back the 3 constant functions. Hence, option D (540).

Q48MCQQuadratic & Polynomial Equations

Let xx, yy, and zz be real numbers satisfying 4(x2+y2+z2)=a,4(x^2 + y^2 + z^2) = a, 4(x−y−z)=3+a4(x - y - z) = 3 + a Then aa equals
  1. 3
  2. 1131\frac{1}{3}
  3. 4
  4. 1
Answer and solution

Answer: (A) 3

Substitute a=4(x2+y2+z2)a = 4(x^2 + y^2 + z^2) from the first equation into the second: 4(x−y−z)=3+4x2+4y2+4z24(x - y - z) = 3 + 4x^2 + 4y^2 + 4z^2 4x2−4x+4y2+4y+4z2+4z+3=04x^2 - 4x + 4y^2 + 4y + 4z^2 + 4z + 3 = 0 Write 33 as 1+1+11 + 1 + 1 and complete the squares: (2x−1)2+(2y+1)2+(2z+1)2=0(2x - 1)^2 + (2y + 1)^2 + (2z + 1)^2 = 0 A sum of squares of real numbers is 0 only if each square is 0, so x=12x = \frac{1}{2}, y=−12y = -\frac{1}{2}, z=−12z = -\frac{1}{2}. Then a=4(14+14+14)=3a = 4\left(\frac{1}{4} + \frac{1}{4} + \frac{1}{4}\right) = 3. The second equation agrees: 4(12+12+12)=6=3+a4\left(\frac{1}{2} + \frac{1}{2} + \frac{1}{2}\right) = 6 = 3 + a. Since xx, yy, zz are forced, aa has no other value; option C, 4, would need x2+y2+z2=1x^2 + y^2 + z^2 = 1, but it is 34\frac{3}{4}. Hence, option A (3).

Q49TITAQuadratic & Polynomial Equations

If the equations x2+mx+9=0x^2 + mx + 9 = 0, x2+nx+17=0x^2 + nx + 17 = 0 and x2+(m+n)x+35=0x^2 + (m+n)x + 35 = 0 have a common negative root, then the value of (2m+3n)(2m + 3n) is

Type in your answer (TITA). No negative mark for a wrong answer.

Answer and solution

Answer: 38

Let α\alpha be the common negative root. Subtract the first equation from the third: (m+n)α+35−mα−9=0(m+n)\alpha + 35 - m\alpha - 9 = 0, so nα=−26n\alpha = -26. Subtract the second equation from the third: (m+n)α+35−nα−17=0(m+n)\alpha + 35 - n\alpha - 17 = 0, so mα=−18m\alpha = -18. Put mα=−18m\alpha = -18 into the first equation: α2−18+9=0\alpha^2 - 18 + 9 = 0, so α2=9\alpha^2 = 9. The root is negative, so α=−3\alpha = -3. Then m=−18−3=6m = \frac{-18}{-3} = 6 and n=−26−3=263n = \frac{-26}{-3} = \frac{26}{3}. Check in the second equation: 9+263(−3)+17=9−26+17=09 + \frac{26}{3}(-3) + 17 = 9 - 26 + 17 = 0. So 2m+3n=12+26=382m + 3n = 12 + 26 = 38. The answer is 38.

Q50MCQSequences & Series

Suppose x1,x2,x3,…,x100x_1, x_2, x_3, \ldots, x_{100} are in arithmetic progression such that x5=−4x_5 = -4 and 2x6+2x9=x11+x132x_6 + 2x_9 = x_{11} + x_{13}. Then, x100x_{100} equals
  1. -194
  2. -196
  3. 204
  4. 206
Answer and solution

Answer: (A) -194

Let the first term be aa and the common difference dd, so xn=a+(n−1)dx_n = a + (n-1)d. 2x6+2x9=x11+x132x_6 + 2x_9 = x_{11} + x_{13} gives 2(a+5d)+2(a+8d)=(a+10d)+(a+12d)2(a + 5d) + 2(a + 8d) = (a + 10d) + (a + 12d). So 4a+26d=2a+22d4a + 26d = 2a + 22d, which gives 2a=−4d2a = -4d, i.e. a=−2da = -2d. x5=a+4d=−4x_5 = a + 4d = -4 gives −2d+4d=−4-2d + 4d = -4, so d=−2d = -2 and a=4a = 4. x100=a+99d=4−198=−194x_{100} = a + 99d = 4 - 198 = -194. Option B, −196-196, comes from using a+100da + 100d instead of a+99da + 99d. Hence, option A (-194).

Q51TITATime & Work

Renu would take 15 days working 4 hours per day to complete a certain task whereas Seema would take 8 days working 5 hours per day to complete the same task. They decide to work together to complete this task. Seema agrees to work for double the number of hours per day as Renu, while Renu agrees to work for double the number of days as Seema. If Renu works 2 hours per day, then the number of days Seema will work, is

Type in your answer (TITA). No negative mark for a wrong answer.

Answer and solution

Answer: 6

Renu alone needs 15×4=6015 \times 4 = 60 hours, so she does 160\frac{1}{60} of the task per hour. Seema alone needs 8×5=408 \times 5 = 40 hours, so she does 140\frac{1}{40} per hour. Let Seema work dd days. Renu works 2 hours a day for 2d2d days, that is 4d4d hours. Seema works 2×2=42 \times 2 = 4 hours a day for dd days, also 4d4d hours. Together they complete the task: 4d60+4d40=1\frac{4d}{60} + \frac{4d}{40} = 1 d15+d10=1\frac{d}{15} + \frac{d}{10} = 1, so 2d+3d30=1\frac{2d + 3d}{30} = 1 and d=6d = 6. Seema works 6 days, and Renu 12 days. The answer is 6.

Q52MCQRemainders

When 1010010^{100} is divided by 7, the remainder is
  1. 3
  2. 4
  3. 1
  4. 6
Answer and solution

Answer: (B) 4

Since 10=7+310 = 7 + 3, 1010010^{100} leaves the same remainder as 31003^{100} when divided by 7. Powers of 3 modulo 7: 31≡33^1 \equiv 3, 32≡23^2 \equiv 2, 33≡63^3 \equiv 6, 34≡43^4 \equiv 4, 35≡53^5 \equiv 5, 36≡13^6 \equiv 1. The remainders repeat every 6 powers. 100=6×16+4100 = 6 \times 16 + 4, so 3100=(36)16×34≡116×4=4(mod7)3^{100} = (3^6)^{16} \times 3^4 \equiv 1^{16} \times 4 = 4 \pmod{7}. So 1010010^{100} leaves remainder 4. Option C, 1, would need the exponent to be a multiple of 6, and 100 is not. Hence, option B (4).

Q53MCQIndices & Surds

The sum of all real values of kk for which (18)k×(132768)13=18×(132768)1k\left(\dfrac{1}{8}\right)^k \times \left(\dfrac{1}{32768}\right)^{\frac{1}{3}} = \dfrac{1}{8} \times \left(\dfrac{1}{32768}\right)^{\frac{1}{k}}, is
  1. 2/3
  2. 4/3
  3. -2/3
  4. -4/3
Answer and solution

Answer: (C) -2/3

32768=215=8532768 = 2^{15} = 8^5, so write every term as a power of 88. Left side: (18)k×(132768)1/3=8−k×8−5/3=8−k−5/3\left(\dfrac{1}{8}\right)^k \times \left(\dfrac{1}{32768}\right)^{1/3} = 8^{-k} \times 8^{-5/3} = 8^{-k - 5/3}. Right side: 18×(132768)1/k=8−1×8−5/k=8−1−5/k\dfrac{1}{8} \times \left(\dfrac{1}{32768}\right)^{1/k} = 8^{-1} \times 8^{-5/k} = 8^{-1 - 5/k}. Equating exponents: k+53=1+5kk + \dfrac{5}{3} = 1 + \dfrac{5}{k}. Multiplying by 3k3k (with k≠0k \ne 0): 3k2+5k=3k+153k^2 + 5k = 3k + 15, so 3k2+2k−15=03k^2 + 2k - 15 = 0. Its discriminant is 22+4×3×15=184>02^2 + 4 \times 3 \times 15 = 184 > 0, so both roots are real, and they are non-zero since their product is −5-5. Their sum is −23-\dfrac{2}{3}. Option A (23\dfrac{2}{3}) has the wrong sign: the sum of the roots of 3k2+2k−15=03k^2 + 2k - 15 = 0 is −23-\dfrac{2}{3}. Hence, option C (-2/3).

Q54TITAFunctions & Graphs

For any natural number nn, let ana_n be the largest integer not exceeding n\sqrt{n}. Then the value of a1+a2+⋯+a50a_1 + a_2 + \cdots + a_{50} is

Type in your answer (TITA). No negative mark for a wrong answer.

Answer and solution

Answer: 217

an=⌊n⌋a_n = \lfloor \sqrt{n} \rfloor stays the same between consecutive perfect squares: an=ka_n = k for k2≤n≤(k+1)2−1k^2 \le n \le (k+1)^2 - 1, which is 2k+12k + 1 values of nn. So, up to n=50n = 50: an=1a_n = 1 for n=1n = 1 to 33 (3 terms), an=2a_n = 2 for n=4n = 4 to 88 (5 terms), an=3a_n = 3 for n=9n = 9 to 1515 (7 terms), an=4a_n = 4 for n=16n = 16 to 2424 (9 terms), an=5a_n = 5 for n=25n = 25 to 3535 (11 terms), an=6a_n = 6 for n=36n = 36 to 4848 (13 terms), and an=7a_n = 7 for n=49,50n = 49, 50 (2 terms). Check: 3+5+7+9+11+13+2=503 + 5 + 7 + 9 + 11 + 13 + 2 = 50 terms. Sum =1×3+2×5+3×7+4×9+5×11+6×13+7×2= 1 \times 3 + 2 \times 5 + 3 \times 7 + 4 \times 9 + 5 \times 11 + 6 \times 13 + 7 \times 2 =3+10+21+36+55+78+14=217= 3 + 10 + 21 + 36 + 55 + 78 + 14 = 217. The answer is 217.

Q55MCQPercentages

In September, the incomes of Kamal, Amal and Vimal are in the ratio 8:6:58 : 6 : 5. They rent a house together, and Kamal pays 15%, Amal pays 12% and Vimal pays 18% of their respective incomes to cover the total house rent in that month. In October, the house rent remains unchanged while their incomes increase by 10%, 12% and 15%, respectively. In October, the percentage of their total income that will be paid as house rent, is nearest to
  1. 15.18
  2. 13.26
  3. 14.84
  4. 12.75
Answer and solution

Answer: (B) 13.26

Take the September incomes as 80x80x, 60x60x and 50x50x (ratio 8:6:58 : 6 : 5). Rent paid: Kamal 15%15\% of 80x=12x80x = 12x, Amal 12%12\% of 60x=7.2x60x = 7.2x, Vimal 18%18\% of 50x=9x50x = 9x. Total rent =28.2x= 28.2x. October incomes: Kamal 1.10×80x=88x1.10 \times 80x = 88x, Amal 1.12×60x=67.2x1.12 \times 60x = 67.2x, Vimal 1.15×50x=57.5x1.15 \times 50x = 57.5x. Total =212.7x= 212.7x. The rent is unchanged, so the share of income paid as rent is 28.2x212.7x≈0.1326\frac{28.2x}{212.7x} \approx 0.1326, about 13.26%13.26\%. Option C, 14.8414.84, is September's share, 28.2x190x≈14.84%\frac{28.2x}{190x} \approx 14.84\%; it ignores the rise in incomes. Hence, option B (13.26).

Q56TITAPermutations & Combinations

The sum of all four-digit numbers that can be formed with the distinct non-zero digits aa, bb, cc, and dd, with each digit appearing exactly once in every number, is 153310+n153310 + n, where nn is a single digit natural number. Then, the value of (a+b+c+d+n)(a + b + c + d + n) is

Type in your answer (TITA). No negative mark for a wrong answer.

Answer and solution

Answer: 31

The 4 distinct digits form 4!=244! = 24 numbers. In each place, each digit appears 3!=63! = 6 times, so the digits in any one place add up to 6(a+b+c+d)6(a + b + c + d). Sum of all the numbers =6(a+b+c+d)(1000+100+10+1)=6666(a+b+c+d)= 6(a + b + c + d)(1000 + 100 + 10 + 1) = 6666(a + b + c + d). This equals 153310+n153310 + n with nn from 1 to 9, so a multiple of 6666 must lie between 153311 and 153319. 6666×23=1533186666 \times 23 = 153318 lies in that range, while 6666×22=1466526666 \times 22 = 146652 and 6666×24=1599846666 \times 24 = 159984 do not. So a+b+c+d=23a + b + c + d = 23 and n=8n = 8. (A sum of 23 is possible with distinct non-zero digits, e.g. 9, 8, 5, 1.) a+b+c+d+n=23+8=31a + b + c + d + n = 23 + 8 = 31. The answer is 31.

Q57TITATriangles & Lines

ABCDABCD is a rectangle with sides AB=56AB = 56 cm and BC=45BC = 45 cm, and EE is the midpoint of side CDCD. Then, the length, in cm, of radius of incircle of △ADE\triangle ADE is

Type in your answer (TITA). No negative mark for a wrong answer.

Answer and solution

Answer: 10

EE is the midpoint of CDCD, and CD=AB=56CD = AB = 56 cm, so DE=28DE = 28 cm. Also AD=BC=45AD = BC = 45 cm. Solution figure for question 57, CAT 2024 Slot 1 Triangle ADEADE has a right angle at DD, a corner of the rectangle, with legs AD=45AD = 45 and DE=28DE = 28. Hypotenuse: AE2=452+282=2025+784=2809AE^2 = 45^2 + 28^2 = 2025 + 784 = 2809, so AE=53AE = 53. For a right triangle with legs pp, qq and hypotenuse hh, the inradius is r=p+q−h2r = \frac{p + q - h}{2}. r=45+28−532=202=10r = \frac{45 + 28 - 53}{2} = \frac{20}{2} = 10. Check with area over semi-perimeter: area =12×45×28=630= \frac{1}{2} \times 45 \times 28 = 630, semi-perimeter =45+28+532=63= \frac{45 + 28 + 53}{2} = 63, and 63063=10\frac{630}{63} = 10. The answer is 10.

Q58MCQCoordinate Geometry

In the XYXY-plane, the area, in sq. units, of the region defined by the inequalities y≥x+4y \geq x + 4 and −4≤x2+y2+4(x−y)≤0-4 \leq x^2 + y^2 + 4(x - y) \leq 0 is
  1. 2π2\pi
  2. 4π4\pi
  3. π\pi
  4. 3π3\pi
Answer and solution

Answer: (A) 2π2\pi

Complete the squares in the middle expression: x2+y2+4x−4y=(x+2)2+(y−2)2−8x^2 + y^2 + 4x - 4y = (x + 2)^2 + (y - 2)^2 - 8. So −4≤(x+2)2+(y−2)2−8≤0-4 \le (x + 2)^2 + (y - 2)^2 - 8 \le 0 means 4≤(x+2)2+(y−2)2≤84 \le (x + 2)^2 + (y - 2)^2 \le 8. This is the ring between two circles centred at (−2,2)(-2, 2) with radii 22 and 222\sqrt{2}. Solution figure for question 58, CAT 2024 Slot 1 The line y=x+4y = x + 4 passes through the centre, since 2=−2+42 = -2 + 4. So it cuts the ring into two equal halves, and y≥x+4y \ge x + 4 keeps the half above the line. Ring area =π(22)2−π(2)2=8π−4π=4π= \pi(2\sqrt{2})^2 - \pi(2)^2 = 8\pi - 4\pi = 4\pi. Required area =12×4π=2π= \frac{1}{2} \times 4\pi = 2\pi. Option B, 4π4\pi, is the whole ring; it ignores the condition y≥x+4y \ge x + 4. Hence, option A (2π2\pi).

Q59TITALogarithms

If xx is a positive real number such that 4log⁡10x+4log⁡100x+8log⁡1000x=134\log_{10} x + 4\log_{100} x + 8\log_{1000} x = 13, then the greatest integer not exceeding xx, is

Type in your answer (TITA). No negative mark for a wrong answer.

Answer and solution

Answer: 31

Change every log to base 10, using log⁡10kx=1klog⁡10x\log_{10^k} x = \frac{1}{k}\log_{10} x: log⁡100x=12log⁡10x\log_{100} x = \frac{1}{2}\log_{10} x and log⁡1000x=13log⁡10x\log_{1000} x = \frac{1}{3}\log_{10} x. The equation becomes 4log⁡10x+2log⁡10x+83log⁡10x=134\log_{10} x + 2\log_{10} x + \frac{8}{3}\log_{10} x = 13. So 263log⁡10x=13\frac{26}{3}\log_{10} x = 13, which gives log⁡10x=32\log_{10} x = \frac{3}{2}. Then x=103/2=1000=1010x = 10^{3/2} = \sqrt{1000} = 10\sqrt{10}. Since 312=961<1000<1024=32231^2 = 961 < 1000 < 1024 = 32^2, we get 31<x<3231 < x < 32 (x≈31.62x \approx 31.62). The greatest integer not exceeding xx is 31. The answer is 31.

Q60MCQProfit, Loss & Discount

The selling price of a product is fixed to ensure 40% profit. If the product had cost 40% less and had been sold for 5 rupees less, then the resulting profit would have been 50%. The original selling price, in rupees, of the product is
  1. 15
  2. 14
  3. 10
  4. 20
Answer and solution

Answer: (B) 14

Let the original cost price be cc. A 40%40\% profit makes the selling price 1.4c1.4c. The new cost price is 40%40\% less, 0.6c0.6c, and the new selling price is 1.4c−51.4c - 5. This gives a 50%50\% profit, so 1.4c−5=1.5×0.6c=0.9c1.4c - 5 = 1.5 \times 0.6c = 0.9c 0.5c=50.5c = 5, so c=10c = 10. Original selling price =1.4×10=14= 1.4 \times 10 = 14 rupees. Check: new cost 66, new price 14−5=914 - 5 = 9, profit 36=50%\frac{3}{6} = 50\%. Option C, 10, is the original cost price, not the selling price. Hence, option B (14).

Q61MCQAverages, Mixtures & Alligations

A glass is filled with milk. Two-thirds of its content is poured out and replaced with water. If this process of pouring out two-thirds the content and replacing with water is repeated three more times, then the final ratio of milk to water in the glass, is
  1. 1:271 : 27
  2. 1:801 : 80
  3. 1:811 : 81
  4. 1:261 : 26
Answer and solution

Answer: (B) 1:801 : 80

Each time two-thirds of the contents is poured out, one-third of the milk present stays; the water only refills the glass. This happens once and then three more times, 4 times in all. Milk left =(1−23)4=(13)4=181= \left(1 - \frac{2}{3}\right)^4 = \left(\frac{1}{3}\right)^4 = \frac{1}{81} of the glass. Water =1−181=8081= 1 - \frac{1}{81} = \frac{80}{81} of the glass. Milk : water =181:8081=1:80= \frac{1}{81} : \frac{80}{81} = 1 : 80. Option C, 1:811 : 81, compares the milk with the whole glass, not with the water. Hence, option B (1:801 : 80).

Q62TITARatios, Proportions & Partnership

A fruit seller has a total of 187 fruits consisting of apples, mangoes and oranges. The number of apples and mangoes are in the ratio 5:25 : 2. After she sells 75 apples, 26 mangoes and half of the oranges, the ratio of number of unsold apples to number of unsold oranges becomes 3:23 : 2. The total number of unsold fruits is

Type in your answer (TITA). No negative mark for a wrong answer.

Answer and solution

Answer: 66

Let the apples be 5x5x and the mangoes 2x2x. Then the oranges are 187−7x187 - 7x. After the sales, 5x−755x - 75 apples and 187−7x2\frac{187 - 7x}{2} oranges remain, in the ratio 3:23 : 2: 5x−75(187−7x)/2=32\frac{5x - 75}{(187 - 7x)/2} = \frac{3}{2} 4(5x−75)=3(187−7x)4(5x - 75) = 3(187 - 7x) 20x−300=561−21x20x - 300 = 561 - 21x, so 41x=86141x = 861 and x=21x = 21. So there were 105 apples, 42 mangoes and 187−147=40187 - 147 = 40 oranges. Unsold: apples 105−75=30105 - 75 = 30, mangoes 42−26=1642 - 26 = 16, oranges 40÷2=2040 \div 2 = 20. Check: 30:20=3:230 : 20 = 3 : 2. Total unsold =30+16+20=66= 30 + 16 + 20 = 66. The answer is 66.

Q63MCQTime, Speed & Distance

Two places AA and BB are 45 kms apart and connected by a straight road. Anil goes from AA to BB while Sunil goes from BB to AA. Starting at the same time, they cross each other in exactly 1 hour 30 minutes. If Anil reaches BB exactly 1 hour 15 minutes after Sunil reaches AA, the speed of Anil, in km per hour, is
  1. 18
  2. 16
  3. 14
  4. 12
Answer and solution

Answer: (D) 12

They meet after 90 minutes. Let Sunil need tt more minutes to reach AA. Anil reaches BB 75 minutes after Sunil reaches AA, so Anil needs t+75t + 75 more minutes. After the meeting, each covers the stretch the other covered in 90 minutes. If their speeds are vAv_A and vSv_S, Anil takes 90vSvA90\frac{v_S}{v_A} minutes and Sunil 90vAvS90\frac{v_A}{v_S}, so the product of these times is 90290^2: t(t+75)=8100t(t + 75) = 8100 t2+75t−8100=0t^2 + 75t - 8100 = 0, i.e. (t−60)(t+135)=0(t - 60)(t + 135) = 0, so t=60t = 60. Anil needs 60+75=13560 + 75 = 135 minutes after the meeting, so his total time is 90+135=22590 + 135 = 225 minutes =3.75= 3.75 hours. Anil's speed =453.75=12= \frac{45}{3.75} = 12 km/h. Option A, 18, is Sunil's speed: his total time is 90+60=15090 + 60 = 150 minutes, and 452.5=18\frac{45}{2.5} = 18 km/h. Hence, option D (12).

Q64TITAAverages, Mixtures & Alligations

There are four numbers such that average of first two numbers is 1 more than the first number, average of first three numbers is 2 more than average of first two numbers, and average of first four numbers is 3 more than average of first three numbers. Then, the difference between the largest and the smallest numbers, is

Type in your answer (TITA). No negative mark for a wrong answer.

Answer and solution

Answer: 15

Call the numbers aa, bb, cc, dd in the given order. a+b2=a+1\frac{a + b}{2} = a + 1 gives b=a+2b = a + 2. a+b+c3=a+b2+2\frac{a + b + c}{3} = \frac{a + b}{2} + 2. Multiply by 6: 2(a+b+c)=3(a+b)+122(a + b + c) = 3(a + b) + 12, so 2c=a+b+12=2a+142c = a + b + 12 = 2a + 14 and c=a+7c = a + 7. a+b+c+d4=a+b+c3+3\frac{a + b + c + d}{4} = \frac{a + b + c}{3} + 3. Multiply by 12: 3(a+b+c+d)=4(a+b+c)+363(a + b + c + d) = 4(a + b + c) + 36, so 3d=a+b+c+36=3a+453d = a + b + c + 36 = 3a + 45 and d=a+15d = a + 15. The numbers are aa, a+2a + 2, a+7a + 7, a+15a + 15. Whatever aa is, the smallest is aa and the largest is a+15a + 15. Their difference is 15. The answer is 15.

Q65MCQSimple & Compound Interest

An amount of Rs 10000 is deposited in bank AA for a certain number of years at a simple interest of 5% per annum. On maturity, the total amount received is deposited in bank BB for another 5 years at a simple interest of 6% per annum. If the interests received from bank AA and bank BB are in the ratio 10:1310 : 13, then the investment period, in years, in bank AA is
  1. 4
  2. 5
  3. 3
  4. 6
Answer and solution

Answer: (D) 6

Let the money stay in bank AA for tt years. Interest from AA: 10000×0.05×t=500t10000 \times 0.05 \times t = 500t. Amount at maturity: 10000+500t10000 + 500t. Interest from BB: (10000+500t)×0.06×5=0.3(10000+500t)=3000+150t(10000 + 500t) \times 0.06 \times 5 = 0.3(10000 + 500t) = 3000 + 150t. The ratio is 10:1310 : 13: 500t3000+150t=1013\frac{500t}{3000 + 150t} = \frac{10}{13} 6500t=30000+1500t6500t = 30000 + 1500t, so 5000t=300005000t = 30000 and t=6t = 6. Check: the interests are 3000 and 0.3×13000=39000.3 \times 13000 = 3900, in the ratio 10:1310 : 13. Option B, 5, gives 2500 and 0.3×12500=37500.3 \times 12500 = 3750, a ratio of 2:32 : 3, not 10:1310 : 13. Hence, option D (6).

Q66MCQLinear Equations

A shop wants to sell a certain quantity (in kg) of grains. It sells half the quantity and an additional 3 kg of these grains to the first customer. Then, it sells half of the remaining quantity and an additional 3 kg of these grains to the second customer. Finally, when the shop sells half of the remaining quantity and an additional 3 kg of these grains to the third customer, there are no grains left. The initial quantity, in kg, of grains is
  1. 50
  2. 36
  3. 42
  4. 18
Answer and solution

Answer: (C) 42

Work backwards from the end. If the shop has RR kg before a customer, it sells R2+3\dfrac{R}{2} + 3 kg and keeps R2−3\dfrac{R}{2} - 3 kg. After the third customer nothing is left: R22−3=0\dfrac{R_2}{2} - 3 = 0, so R2=6R_2 = 6 kg before the third customer. Before the second customer: R12−3=6\dfrac{R_1}{2} - 3 = 6, so R1=18R_1 = 18 kg. At the start: N2−3=18\dfrac{N}{2} - 3 = 18, so N=42N = 42 kg. Check: from 4242 the shop sells 21+3=2421 + 3 = 24 and keeps 1818; then sells 9+3=129 + 3 = 12 and keeps 66; then sells 3+3=63 + 3 = 6 and keeps 00. Option D (18) is the stock before the second customer, not the initial quantity. Option B (36) fails the check: it leaves 1515, then 4.54.5, and the third customer would need 5.255.25 kg. Hence, option C (42).

Q67MCQIndices & Surds

If (a+bn)(a + b\sqrt{n}) is the positive square root of (29−125)(29 - 12\sqrt{5}), where aa and bb are integers, and nn is a natural number, then the maximum possible value of (a+b+n)(a + b + n) is
  1. 18
  2. 22
  3. 4
  4. 6
Answer and solution

Answer: (A) 18

Try to write 29−12529 - 12\sqrt{5} as a perfect square: (3−25)2=9+20−125=29−125(3 - 2\sqrt{5})^2 = 9 + 20 - 12\sqrt{5} = 29 - 12\sqrt{5}. Since 25≈4.47>32\sqrt{5} \approx 4.47 > 3, the positive square root is 25−32\sqrt{5} - 3. So a+bn=−3+25a + b\sqrt{n} = -3 + 2\sqrt{5}. The rational parts must match, so a=−3a = -3 and bn=25=20b\sqrt{n} = 2\sqrt{5} = \sqrt{20}. With bb an integer and nn natural, this allows b=2,n=5b = 2, n = 5, giving a+b+n=4a + b + n = 4, or b=1,n=20b = 1, n = 20, giving a+b+n=18a + b + n = 18. The maximum is 18. The option 4 is the trap of stopping at the first form. Hence, option A (18).

Q68MCQMensuration

The surface area of a closed rectangular box, which is inscribed in a sphere, is 846 sq cm, and the sum of the lengths of all its edges is 144 cm. The volume, in cubic cm, of the sphere is
  1. 1125π1125\pi
  2. 750π750\pi
  3. 1125π21125\pi\sqrt{2}
  4. 750π2750\pi\sqrt{2}
Answer and solution

Answer: (C) 1125π21125\pi\sqrt{2}

Let the box have edges ll, bb, hh. Edges: 4(l+b+h)=1444(l + b + h) = 144, so l+b+h=36l + b + h = 36. Surface area: 2(lb+bh+hl)=8462(lb + bh + hl) = 846. So l2+b2+h2=(l+b+h)2−2(lb+bh+hl)=1296−846=450l^2 + b^2 + h^2 = (l + b + h)^2 - 2(lb + bh + hl) = 1296 - 846 = 450. Solution figure for question 68, CAT 2024 Slot 1 The box is inscribed in the sphere, so its space diagonal is a diameter: l2+b2+h2=2R\sqrt{l^2 + b^2 + h^2} = 2R. Then 4R2=4504R^2 = 450, R2=2252R^2 = \frac{225}{2} and R=152R = \frac{15}{\sqrt{2}}. Volume =43πR3=43π×337522=2250π2=1125π2= \frac{4}{3}\pi R^3 = \frac{4}{3}\pi \times \frac{3375}{2\sqrt{2}} = \frac{2250\pi}{\sqrt{2}} = 1125\pi\sqrt{2}. Option A, 1125π1125\pi, drops the factor 2\sqrt{2}; it stays because R=152R = \frac{15}{\sqrt{2}} is irrational, so R3R^3 carries it. Hence, option C (1125π21125\pi\sqrt{2}).