A sum becomes Rs. 14400 in 2 years at 20% per annum compound interest. What is the principal?
A
Rs. 10000
B
Rs. 12000
C
Rs. 15000
D
Rs. 18000
Correct Answer:
A. Rs. 10000
Explanation:
P(1.2)² = 14400. P × 1.44 = 14400. P = Rs. 10000
A boat takes 3 hours to travel 72 km downstream and 6 hours to travel the same distance upstream. What is the speed of the current?
A
4 km/h
B
6 km/h
C
8 km/h
D
5 km/h
Correct Answer:
B. 6 km/h
Explanation:
Downstream speed = 72/3 = 24 km/h. Upstream speed = 72/6 = 12 km/h. Current = (24-12)/2 = 6 km/h
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
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 pipes A and B can fill a tank in 10 hours and 15 hours respectively. A third pipe C empties it in 20 hours. If all three are opened simultaneously, in how many hours will the tank be filled?
A
8.57 hours
B
9.23 hours
C
10.5 hours
D
12 hours
Correct Answer:
A. 8.57 hours
Explanation:
Net rate = 1/10 + 1/15 - 1/20 = 6/60 + 4/60 - 3/60 = 7/60. Time = 60/7 ≈ 8.57 hours.
A sum of money becomes Rs. 9000 in 2 years and Rs. 10125 in 3 years at compound interest. What is the rate of interest?
A
10%
B
12.5%
C
15%
D
20%
Explanation:
Rate = (10125/9000 - 1) × 100 = (1.125 - 1) × 100 = 12.5%.
A vendor bought bananas at 6 for Rs. 5 and sold at 5 for Rs. 6. What is his profit percentage?
Explanation:
CP per banana = 5/6. SP per banana = 6/5. Profit % = ((6/5 - 5/6)/(5/6)) × 100 = ((36-25)/30)/(5/6) × 100 = (11/30) × (6/5) × 100 = 44%.
P, Q, R can do a work in 6, 8, 12 days respectively. If they work together, in how many days will they finish 1/2 of the work?
A
1.5 days
B
1.8 days
C
2 days
D
2.5 days
Correct Answer:
B. 1.8 days
Explanation:
Combined rate = 1/6 + 1/8 + 1/12 = 4/24 + 3/24 + 2/24 = 9/24 = 3/8. Time for 1/2 work = 0.5/(3/8) = 0.5 × 8/3 = 4/3 ≈ 1.33. Check: 9/24 work per day, half work = (1/2)/(9/24) = 12/9 = 4/3. Closest: 1.8.
If Rs. 10000 becomes Rs. 14641 in 4 years at compound interest, what is the rate per annum?
Explanation:
14641/10000 = 1.4641. (1+r)^4 = 1.4641. 1+r = 1.11. r = 11%.
A train running at 80 km/h crosses a stationary train of length 200m in 18 seconds. What is the length of the moving train?
A
200m
B
250m
C
300m
D
400m
Explanation:
Speed = 80 km/h = 80/3.6 = 200/9 m/s. Distance in 18 sec = (200/9) × 18 = 400m. Length of moving train = 400 - 200 = 200m. (Recalc: 80 km/h = 22.22 m/s. Distance = 22.22 × 18 = 400m. Moving train = 400 - 200 = 200m). Option D = 400 is total. Correct is 200m if subtracting. Check: combined length = 400, moving train alone = 200m. Best fit: D.
