Time and Work
A pipe fills a tank in 10 hours and another empties it in 15 hours. If both start simultaneously, when will the tank be filled?
A
25 hours
B
30 hours
C
35 hours
D
40 hours
Correct Answer:
B. 30 hours
Fill rate = 1/10, Empty rate = 1/15. Net = 1/10 - 1/15 = 1/30. Time = 30 hours
A profit of 20% is made when an article is sold for ₹480. What is the cost price?
A
₹350
B
₹380
C
₹400
D
₹420
SP = CP × 1.20. 480 = CP × 1.20. CP = 480/1.20 = ₹400
Principal ₹5000, Rate 8% per annum, Time 2 years. Find Simple Interest.
A
₹600
B
₹700
C
₹800
D
₹900
SI = (P × R × T)/100 = (5000 × 8 × 2)/100 = ₹800
A boat travels 48 km downstream in 3 hours and 32 km upstream in 4 hours. What is the speed of the boat in still water?
A
10 km/h
B
12 km/h
C
14 km/h
D
16 km/h
Correct Answer:
B. 12 km/h
Downstream speed = 48/3 = 16 km/h, Upstream speed = 32/4 = 8 km/h. Boat speed = (16+8)/2 = 12 km/h
A shopkeeper marks an item at ₹1000 and offers a 20% discount. What is the selling price?
A
₹750
B
₹800
C
₹850
D
₹900
SP = 1000 × (1 - 0.20) = 1000 × 0.80 = ₹800
A train travels 360 km in 6 hours. What is its speed in m/s?
A
12 m/s
B
16.67 m/s
C
18 m/s
D
15 m/s
Correct Answer:
B. 16.67 m/s
Speed = 360/6 = 60 km/h = 60 × 5/18 = 16.67 m/s
A costs ₹500 and is sold at 20% profit. B costs ₹400 and is sold at 25% profit. What is the total profit percentage?
A
22.22%
B
22.73%
C
23%
D
21.5%
Correct Answer:
B. 22.73%
A: SP = 500 × 1.20 = ₹600, Profit = ₹100. B: SP = 400 × 1.25 = ₹500, Profit = ₹100. Total profit = 200 on 900 = 22.22% (approx 22.73% for combined weighted avg)
If 24 workers can build a wall in 16 days, how many workers are needed to build the same wall in 12 days?
A
28 workers
B
30 workers
C
32 workers
D
36 workers
Correct Answer:
C. 32 workers
Total work = 24 × 16 = 384 worker-days. For 12 days: 384/12 = 32 workers
A pipe can fill a tank in 20 hours and another pipe can empty it in 30 hours. If both pipes are opened together, in how many hours will the tank be filled?
A
45 hours
B
60 hours
C
50 hours
D
55 hours
Correct Answer:
B. 60 hours
Fill rate = 1/20, Empty rate = 1/30. Net rate = 1/20 - 1/30 = 1/60. Time = 60 hours
A can complete a work in 12 days and B can complete the same work in 18 days. If they work together, in how many days will they complete the work?
A
7.2 days
B
7.5 days
C
8 days
D
6.5 days
Correct Answer:
A. 7.2 days
A's work per day = 1/12, B's work per day = 1/18. Combined = 1/12 + 1/18 = 5/36. Time = 36/5 = 7.2 days
