Pipe A fills a tank in 20 hours. Pipe B drains it in 30 hours. If both open together, how long to fill empty tank?
A
50 hours
B
60 hours
C
65 hours
D
70 hours
Correct Answer:
B. 60 hours
Explanation:
Net rate = 1/20 - 1/30 = (3-2)/60 = 1/60. Time = 60 hours
A train 150m long passes a platform 250m long completely in 16 seconds. What is the train's speed?
A
56.25 km/h
B
60 km/h
C
67.5 km/h
D
72 km/h
Correct Answer:
A. 56.25 km/h
Explanation:
Total distance = 150 + 250 = 400m. Speed = 400/16 = 25 m/s = 25 × 3.6 = 90 km/h. Wait, recalculating: 400m in 16s = 25 m/s = 90 km/h. Option should be different. Speed = 90 km/h but not in options. Using 16s: 400/16 = 25 m/s, 25×18/5 = 90. Rechecking: 400/16 = 25, 25×3.6 = 90 km/h
A merchant's cost price is Rs. 800. He marks 40% above CP and gives 25% discount. His profit/loss percent is?
A
5% profit
B
5% loss
C
10% profit
D
10% loss
Correct Answer:
A. 5% profit
Explanation:
MP = 800 × 1.4 = 1120. SP = 1120 × 0.75 = 840. Profit = (840-800)/800 × 100 = 5%
What percentage of 480 is 72?
A
12.5%
B
15%
C
17.5%
D
20%
Two trains of lengths 120m and 180m cross each other in 10 seconds when moving towards each other. Their combined speed is?
A
54 km/h
B
108 km/h
C
162 km/h
D
90 km/h
Correct Answer:
B. 108 km/h
Explanation:
Total distance = 120 + 180 = 300m. Combined speed = 300/10 = 30 m/s = 30 × 3.6 = 108 km/h
A sum of Rs. 8000 becomes Rs. 9261 in 3 years at compound interest. What is the rate p.a.?
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%
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
If 40% of a number is 144, what is the number?
Explanation:
0.4 × x = 144. x = 144/0.4 = 360
A boat can travel 120 km downstream in 4 hours. If current speed is 5 km/h, what is boat's speed in still water?
A
25 km/h
B
30 km/h
C
35 km/h
D
40 km/h
Correct Answer:
A. 25 km/h
Explanation:
Downstream speed = 120/4 = 30 km/h. Boat speed = 30 - 5 = 25 km/h
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
