Maths MCQs for AD (ASF) – Series 4 (Q71-80)
Q71. Two numbers are in the ratio 3:4. If 10 is subtracted from each, the ratio becomes 1:2. Find the numbers.
- A) 18 and 24
- B) 15 and 20
- C) 12 and 16
- D) None of these
Answer: B
(3x−10)/(4x−10) = 1/2 → 2(3x−10) = 4x−10 → x = 5; numbers = 15 and 20.
Q72. A sum of Rs. 2400 is divided among A, B and C in the ratio 2:3:5. Find C’s share.
- A) Rs. 1000
- B) Rs. 1400
- C) Rs. 1200
- D) None of these
Answer: C
Total parts = 10; C’s share = (5/10)×2400 = Rs. 1200.
Q73. The average of 20 numbers is 15. If each number is multiplied by 3, find the new average.
- A) 60
- B) 45
- C) 15
- D) None of these
Answer: B
New average = old average × 3 = 15×3 = 45.
Q74. The average weight of 8 boys is 45 kg. A boy weighing 53 kg leaves and another weighing 37 kg joins. Find the new average weight.
- A) 44 kg
- B) 43 kg
- C) 42 kg
- D) None of these
Answer: B
Total = 8×45 = 360; new total = 360−53+37 = 344; new average = 344/8 = 43 kg.
Q75. A mixture contains milk and water in the ratio 5:2. If 14 litres of water is added, the ratio becomes 5:4. Find the initial quantity of milk.
- A) 35 litres
- B) 40 litres
- C) 30 litres
- D) None of these
Answer: A
Let milk = 5x, water = 2x. (2x+14)/5x = 4/5 → 10x+70 = 20x → x = 7; milk = 35 litres.
Q76. The ratio of the present ages of two persons is 5:6. Eight years hence, the ratio will be 7:8. Find the sum of their present ages.
- A) 44 years
- B) 48 years
- C) 40 years
- D) None of these
Answer: A
(5x+8)/(6x+8) = 7/8 → 40x+64 = 42x+56 → x = 4; ages = 20 and 24; sum = 44.
Q77. The average of 5 consecutive odd numbers is 61. Find the largest number.
- A) 65
- B) 67
- C) 63
- D) None of these
Answer: A
The average equals the middle (3rd) term, 61; the largest number is 61+4 = 65.
Q78. A, B and C invest capital in the ratio 4:5:6. If the total profit is Rs. 4500, find B’s share.
- A) Rs. 1200
- B) Rs. 1800
- C) Rs. 1500
- D) None of these
Answer: C
Total parts = 15; B’s share = (5/15)×4500 = Rs. 1500.
Q79. Two numbers are in the ratio 3:5. If each is increased by 10, the ratio becomes 5:7. Find the numbers.
- A) 18 and 30
- B) 9 and 15
- C) 15 and 25
- D) None of these
Answer: C
(3x+10)/(5x+10) = 5/7 → 21x+70 = 25x+50 → x = 5; numbers = 15 and 25.
Q80. The average marks of 30 students in a class is 68. If the average of the first 18 students is 65, find the average of the remaining 12 students.
- A) 72.5
- B) 75
- C) 70
- D) None of these
Answer: A
Total = 30×68 = 2040; first 18 = 18×65 = 1170; remaining 12 total = 870; average = 870/12 = 72.5.
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