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Quantitative Aptitude

Quantitative aptitude questions for competitive exams

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Difficulty: All Easy Medium Hard 81–90 of 429
Topics in Quantitative Aptitude
Q.81 Easy Time and Work
A train of length 200m crosses a platform of length 400m in 30 seconds. What is the speed of the train?
A 20 m/s
B 25 m/s
C 30 m/s
D 35 m/s
Correct Answer:  A. 20 m/s
EXPLANATION

Total distance = train length + platform length = 200 + 400 = 600m. Speed = 600/30 = 20 m/s.

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Q.82 Easy Time and Work
₹10,000 is invested at 10% per annum simple interest. What will be the amount after 3 years?
A ₹12,000
B ₹13,000
C ₹13,310
D ₹14,000
Correct Answer:  B. ₹13,000
EXPLANATION

SI = (P × R × T)/100 = (10000 × 10 × 3)/100 = 3000. Amount = 10000 + 3000 = ₹13,000.

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Q.83 Easy Time and Work
A boat travels 60 km downstream in 3 hours and 60 km upstream in 4 hours. What is the speed of the boat in still water?
A 17.5 km/h
B 15 km/h
C 20 km/h
D 22.5 km/h
Correct Answer:  A. 17.5 km/h
EXPLANATION

Downstream speed = 60/3 = 20 km/h. Upstream speed = 60/4 = 15 km/h. Speed of boat = (20+15)/2 = 35/2 = 17.5 km/h.

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Q.84 Easy Time and Work
Two workers A and B are paid ₹500 and ₹600 per day respectively. If A completes a job in 24 days and B completes it in 18 days, who is more cost-effective?
A A is more cost-effective
B B is more cost-effective
C Both are equally cost-effective
D Cannot be determined
Correct Answer:  B. B is more cost-effective
EXPLANATION

Total cost for A = 500 × 24 = ₹12,000. Total cost for B = 600 × 18 = ₹10,800. B costs less, so B is more cost-effective.

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Q.85 Easy Time and Work
If a number is increased by 25%, and then decreased by 20%, what is the net change?
A 5% increase
B 2% decrease
C 1% increase
D No change
Correct Answer:  A. 5% increase
EXPLANATION

Let original number = 100. After 25% increase = 125. After 20% decrease of 125 = 125 × 0.8 = 100. Wait, let me recalculate: 125 × (100-20)/100 = 125 × 80/100 = 100. Net change = 0. Actually answer is D (No change). Let me verify: 1.25 × 0.8 = 1. So net is no change. Correction: The answer should be D.

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Q.86 Easy Time and Work
A pipe can fill a tank in 15 hours. Another pipe can empty it in 20 hours. If both pipes are opened together, in how many hours will the tank be filled?
A 45 hours
B 50 hours
C 60 hours
D 75 hours
Correct Answer:  C. 60 hours
EXPLANATION

Filling rate = 1/15 per hour. Emptying rate = 1/20 per hour. Net rate = 1/15 - 1/20 = (4-3)/60 = 1/60. Time = 60 hours.

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Q.87 Easy Time and Work
A and B together can complete a work in 12 days. A alone can complete it in 20 days. In how many days can B alone complete the work?
A 25 days
B 30 days
C 35 days
D 40 days
Correct Answer:  B. 30 days
EXPLANATION

Work done by A in 1 day = 1/20. Work done by A+B in 1 day = 1/12. So B's work in 1 day = 1/12 - 1/20 = (5-3)/60 = 2/60 = 1/30. Therefore B takes 30 days.

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Q.88 Easy Time and Work
A man buys bananas at ₹30 per dozen and sells them at ₹3 per banana. What is his profit percentage?
A 15%
B 18%
C 20%
D 25%
Correct Answer:  C. 20%
EXPLANATION

CP per banana = 30/12 = 2.5. SP per banana = 3. Profit = 0.5. Percentage = (0.5/2.5) × 100 = 20%

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Q.89 Easy Time and Work
If a number is increased by 15%, it becomes 299. What is the original number?
A 250
B 260
C 270
D 280
Correct Answer:  B. 260
EXPLANATION

Let original = x. x × 1.15 = 299. x = 299/1.15 = 260

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Q.90 Easy Time and Work
A pipe fills a tank in 20 minutes. A drain empties it in 30 minutes. If both are opened, in how much time will the tank be filled?
A 50 minutes
B 60 minutes
C 70 minutes
D 80 minutes
Correct Answer:  B. 60 minutes
EXPLANATION

Fill rate = 1/20, Drain rate = 1/30. Net rate = 1/20 - 1/30 = 3/60 - 2/60 = 1/60. Time = 60 minutes

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