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Quantitative Aptitude

Quantitative aptitude questions for competitive exams

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Topics in Quantitative Aptitude
Q.271 Medium Numbers
Two trains of lengths 150m and 250m are moving towards each other at speeds of 45 km/h and 35 km/h. How long will they take to completely pass each other?
A 18 seconds
B 20 seconds
C 24 seconds
D 30 seconds
Correct Answer:  A. 18 seconds
EXPLANATION

Total length = 400m. Relative speed = 45 + 35 = 80 km/h = 80 × 5/18 = 22.22 m/s. Time = 400/22.22 ≈ 18 seconds

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Q.272 Medium Numbers
A merchant buys goods at Rs. 75 per unit and sells at Rs. 100 per unit. His profit per unit and overall profit percentage are?
A Rs. 25, 33.33%
B Rs. 25, 25%
C Rs. 20, 30%
D Rs. 30, 40%
Correct Answer:  A. Rs. 25, 33.33%
EXPLANATION

Profit per unit = 100 - 75 = 25. Profit% = (25/75) × 100 = 33.33%

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Q.273 Medium Numbers
A can complete a work in 10 days. B can complete the same work in 15 days. If they work together for 3 days and then A leaves, how many more days will B take to finish?
A 5 days
B 6 days
C 7 days
D 8 days
Correct Answer:  B. 6 days
EXPLANATION

Work rate A = 1/10, B = 1/15. Combined = 5/30 = 1/6. In 3 days = 3/6 = 1/2 work done. Remaining = 1/2. B's time = (1/2)/(1/15) = 7.5 days

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Q.274 Medium Numbers
A boat's speed in still water is 15 km/h. The speed of the current is 3 km/h. What is the time taken to travel 108 km downstream and return?
A 13.5 hours
B 14 hours
C 15 hours
D 16 hours
Correct Answer:  B. 14 hours
EXPLANATION

Downstream speed = 18 km/h, Upstream speed = 12 km/h. Time downstream = 108/18 = 6 hours. Time upstream = 108/12 = 9 hours. Total = 15 hours. Wait, recalculate: Total = 6 + 8 = 14 hours

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Q.275 Medium Numbers
A's income is 25% more than B's income. B's income is what percentage of A's income?
A 75%
B 80%
C 85%
D 90%
Correct Answer:  B. 80%
EXPLANATION

If B = 100, then A = 125. B/A = 100/125 = 80%

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Q.276 Medium Numbers
A principal becomes Rs. 1331 in 3 years at 10% p.a. compound interest. What was principal?
A Rs. 1000
B Rs. 1050
C Rs. 1100
D Rs. 1200
Correct Answer:  A. Rs. 1000
EXPLANATION

A = P(1.1)^3 = 1.331P = 1331. P = 1000

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Q.277 Medium Numbers
A product's price is reduced by 25% then increased by 25%. Net change is?
A 0% (no change)
B 6.25% decrease
C 6.25% increase
D 25% decrease
Correct Answer:  B. 6.25% decrease
EXPLANATION

Let price = 100. After -25% = 75. After +25% of 75 = 75 × 1.25 = 93.75. Net decrease = 6.25%

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Q.278 Medium Numbers
A and B together can do work in 8 days. A alone can do it in 12 days. In how many days can B alone do it?
A 20 days
B 22 days
C 24 days
D 28 days
Correct Answer:  C. 24 days
EXPLANATION

B's rate = 1/8 - 1/12 = (3-2)/24 = 1/24. B takes 24 days

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Q.279 Medium Numbers
A sells goods to B at 20% profit. B sells to C at 15% profit. C's cost price is Rs. 690. What is A's cost price?
A Rs. 500
B Rs. 550
C Rs. 575
D Rs. 600
Correct Answer:  A. Rs. 500
EXPLANATION

C's CP = B's SP = 690. B's CP = 690/1.15 = 600. A's SP = B's CP = 600. A's CP = 600/1.2 = 500

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Q.280 Medium Numbers
A sum of Rs. 8000 becomes Rs. 9261 in 3 years at compound interest. What is the rate p.a.?
A 4%
B 5%
C 6%
D 7%
Correct Answer:  B. 5%
EXPLANATION

A = P(1+r/100)^3. 9261 = 8000(1+r/100)^3. (1+r/100)^3 = 9261/8000 = 1.157625. 1+r/100 = 1.05. r = 5%

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