X and Y together can complete a work in 18 days. X alone can complete it in 30 days. In how many days can Y alone complete the work?
A
45 days
B
38 days
C
42 days
D
35 days
Correct Answer:
A. 45 days
Explanation:
Y's rate = 1/18 - 1/30 = 5/90 - 3/90 = 2/90 = 1/45. Y can complete in 45 days
Rs. 1000 is invested at 10% per annum compound interest for 2 years. What is the final amount?
A
Rs. 1210
B
Rs. 1200
C
Rs. 1100
D
Rs. 1320
Correct Answer:
A. Rs. 1210
Explanation:
Amount = 1000(1 + 10/100)² = 1000 × 1.1 × 1.1 = Rs. 1210
A boat goes 30 km upstream in 6 hours and 30 km downstream in 3 hours. What is the speed of the boat in still water?
A
7.5 km/h
B
6.5 km/h
C
8 km/h
D
5 km/h
Correct Answer:
A. 7.5 km/h
Explanation:
Upstream speed = 30/6 = 5 km/h. Downstream speed = 30/3 = 10 km/h. Boat speed = (5+10)/2 = 7.5 km/h
A product's price increased by 25%, then decreased by 20%. What is the net change?
A
0% (no change)
B
+5%
C
-5%
D
+10%
Explanation:
Let original price = 100. After 25% increase = 125. After 20% decrease = 125 × 80/100 = 100. Net = +5% gain
Three pipes A, B, and C can fill a tank in 6, 8, and 12 hours respectively. If all three are opened together, what fraction of the tank is filled in 1 hour?
A
9/24
B
12/24
C
15/24
D
18/24
Explanation:
Combined rate = 1/6 + 1/8 + 1/12 = 4/24 + 3/24 + 2/24 = 9/24
A train 180m long crosses another train 220m long coming towards it in 9 seconds. If the first train's speed is 40 km/h, what is the speed of the second train?
A
50 km/h
B
32 km/h
C
48 km/h
D
36 km/h
Correct Answer:
B. 32 km/h
Explanation:
Total distance = 180 + 220 = 400m. Relative speed = 400/9 m/s = 160 km/h. Speed of second train = 160 - 40 = 32 km/h
A man sells an item for Rs. 1200 at 20% profit. What is the cost price?
A
Rs. 1000
B
Rs. 900
C
Rs. 1100
D
Rs. 960
Correct Answer:
A. Rs. 1000
Explanation:
CP = 1200 × 100/120 = Rs. 1000
A cistern has a drain pipe that empties it in 20 hours. If an inlet pipe fills it in 15 hours, how long will it take to fill if both are open?
A
60 hours
B
45 hours
C
50 hours
D
55 hours
Correct Answer:
A. 60 hours
Explanation:
Net rate = 1/15 - 1/20 = 4/60 - 3/60 = 1/60. Time = 60 hours
A merchant bought goods for Rs. 8000. He marked them 50% above cost price but gave a discount of 10%. What is his profit?
A
Rs. 1200
B
Rs. 1400
C
Rs. 1600
D
Rs. 1800
Correct Answer:
C. Rs. 1600
Explanation:
Marked Price = 8000 × 150/100 = 12000. Selling Price = 12000 × 90/100 = 10800. Profit = 10800 - 8000 = Rs. 1600
Two taps A and B can fill a tank in 20 and 30 minutes respectively. A third tap C empties it in 40 minutes. If all three are opened together, in how many minutes will the tank be full?
A
15 minutes
B
17.14 minutes
C
18 minutes
D
19 minutes
Correct Answer:
B. 17.14 minutes
Explanation:
Net rate = 1/20 + 1/30 - 1/40 = 6/120 + 4/120 - 3/120 = 7/120. Time = 120/7 ≈ 17.14 minutes
