A tank can be filled by pipe A in 20 hours and by pipe B in 30 hours. Both pipes are opened for 10 hours, then pipe A is closed. How long will pipe B take to fill the remaining tank?
A 5 hours
B 7.5 hours
C 10 hours
D 12 hours
Correct Answer:
A. 5 hours Explanation:
Rate A = 1/20, Rate B = 1/30. Combined = 5/60. In 10 hours = 50/60. Remaining = 10/60. B's time = (10/60)/(1/30) = 5 hours
A sum becomes Rs. 2420 in 2 years at 10% p.a. simple interest. What was the original sum?
A Rs. 2000
B Rs. 2100
C Rs. 2200
D Rs. 2500
Correct Answer:
A. Rs. 2000 Explanation:
A = P + SI = P + (P × 10 × 2)/100 = P × 1.2. 2420 = P × 1.2. P = 2000
A retailer marks goods 50% above cost price. He gives 20% discount on marked price. What is net profit percentage?
Explanation:
Let CP = 100. MP = 150. SP = 150 × 0.8 = 120. Profit% = 20%
A percentage increase of 25% followed by a percentage decrease of 20% results in a net change of?
A No change
B 5% increase
C 5% decrease
D 10% increase
Correct Answer:
B. 5% increase Explanation:
Let value = 100. After 25% increase = 125. After 20% decrease = 125 × 0.8 = 100. Net = 0%. Recalculate: 125 × 0.8 = 100. No wait: 125 × 0.8 = 100. Check: 5% increase option seems wrong. Answer is no change
A sum becomes Rs. 3600 in 3 years at 10% p.a. compound interest. What's the principal?
A Rs. 2500
B Rs. 2703.67
C Rs. 3000
D Rs. 2840
Correct Answer:
B. Rs. 2703.67 Explanation:
A = P(1 + R/100)^T. 3600 = P(1.1)^3 = P(1.331). P = 3600/1.331 ≈ Rs. 2703.67.
A trader marks goods 40% above cost price and gives 10% discount. What's his profit%?
Explanation:
Let CP = 100. MP = 140. SP = 140 × 0.9 = 126. Profit% = (126-100)/100 × 100 = 26%.
A's income is 25% more than B's. By what % is B's income less than A's?
Explanation:
Let B's income = 100, A's = 125. B's is less by 25/125 × 100 = 20%.
A can do 1/3 of work in 5 days. How many days for complete work?
A 10 days
B 12 days
C 15 days
D 18 days
Correct Answer:
C. 15 days Explanation:
If 1/3 work = 5 days, then full work = 5 × 3 = 15 days.
P and Q working together can finish work in 8 days. P alone in 12 days. Q alone takes?
A 20 days
B 24 days
C 18 days
D 16 days
Correct Answer:
B. 24 days Explanation:
Combined rate = 1/8. P's rate = 1/12. Q's rate = 1/8 - 1/12 = 1/24. Q takes 24 days.
A train travels 240 km in 4 hours. What's its speed in m/s?
A 16.67 m/s
B 20 m/s
C 15 m/s
D 18.5 m/s
Correct Answer:
A. 16.67 m/s Explanation:
Speed = 240/4 = 60 km/h = 60 × 5/18 = 16.67 m/s.
