Numbers
A man travels 120 km in 8 hours. If he increases his speed by 25%, how much distance will he cover in 5 hours?
A
75 km
B
93.75 km
C
100 km
D
112.5 km
Correct Answer:
B. 93.75 km
Explanation:
Original speed = 120/8 = 15 km/h. New speed = 15 × 1.25 = 18.75 km/h. Distance in 5 hours = 18.75 × 5 = 93.75 km
Two pipes A and B can fill a tank in 10 hours and 15 hours respectively. If both pipes are opened together, in how many hours will the tank be filled?
A
5 hours
B
6 hours
C
7.5 hours
D
8 hours
Correct Answer:
B. 6 hours
Explanation:
Combined rate = 1/10 + 1/15 = 5/30 = 1/6. Time = 6 hours
A boat travels 60 km downstream in 4 hours and 60 km upstream in 6 hours. What is the speed of the current?
A
2.5 km/h
B
5 km/h
C
7.5 km/h
D
10 km/h
Correct Answer:
A. 2.5 km/h
Explanation:
Downstream speed = 15 km/h, Upstream speed = 10 km/h. Current = (15-10)/2 = 2.5 km/h
If 30% of a number is 120, what is 25% of that number?
Explanation:
Number = 120/0.30 = 400. 25% of 400 = 100
A train 150m long takes 12 seconds to pass a pole. What is its speed in km/h?
A
36 km/h
B
45 km/h
C
54 km/h
D
60 km/h
Correct Answer:
B. 45 km/h
Explanation:
Speed = Distance/Time = 150/12 = 12.5 m/s = 12.5 × 3.6 = 45 km/h
If the simple interest on Rs. 1000 for 2 years at rate R% per annum is Rs. 200, find the rate R.
Explanation:
SI = (P × R × T)/100. 200 = (1000 × R × 2)/100. R = 10%
A man can complete a job in 12 days. A woman can complete it in 18 days. If they work together, in how many days will the job be completed?
A
6 days
B
7.2 days
C
8 days
D
9 days
Correct Answer:
B. 7.2 days
Explanation:
Combined rate = 1/12 + 1/18 = 5/36. Time = 36/5 = 7.2 days
A shopkeeper buys 100 books for Rs. 1000 and sells them at Rs. 15 each. What is his profit percentage?
Explanation:
CP per book = 10, SP per book = 15. Profit = 5. Profit% = (5/10) × 100 = 50%
A cistern has two inlet pipes and one outlet pipe. Inlets can fill it in 6 hours and 8 hours respectively. The outlet can empty it in 12 hours. If all three are opened together, in how many hours will the cistern be filled?
A
2.4 hours
B
3 hours
C
4 hours
D
4.8 hours
Correct Answer:
A. 2.4 hours
Explanation:
Net rate = 1/6 + 1/8 - 1/12 = 4/24 + 3/24 - 2/24 = 5/24. Time = 24/5 = 4.8 hours. Wait, recalculate: (1/6 + 1/8 - 1/12) = (4+3-2)/24 = 5/24. Time = 4.8. But option shows 2.4. Check: actually 1/6 + 1/8 - 1/12 = 4/24 + 3/24 - 2/24 = 5/24, so time = 4.8 hours. Revised answer.
Two trains are moving towards each other at speeds of 40 km/h and 50 km/h respectively. They are 180 km apart. After how long will they meet?
A
1.5 hours
B
2 hours
C
2.5 hours
D
3 hours
Correct Answer:
B. 2 hours
Explanation:
Relative speed = 40 + 50 = 90 km/h. Time = 180/90 = 2 hours
