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?

The correct answer is B: 60 hours. Fill rate = 1/20, Empty rate = 1/30. Net rate = 1/20 - 1/30 = 1/60. Time = 60 hours

A principal of ₹8000 becomes ₹9261 in 3 years at compound interest. Find the rate p.a.

The correct answer is A: 5% p.a.. 9261 = 8000(1+r/100)³; 9261/8000 = (1+r/100)³; 1.157625 ≈ (1.05)³ = 1.157625; r = 5%

A person invests ₹5,000 at 6% per annum simple interest. After how many years will the amount become ₹6,500?

The correct answer is C: 5 years. Step 1: Identify the given values Principal (P) = ₹5,000, Rate (R) = 6% per annum, Final Amount (A) = ₹6,500 $$P = 5000, \quad R = 6\%, \quad A = 6500$$ Step 2: Calculate the Simple Interest Simple Interest (SI) = Final Amount - Principal $$SI = A - P = 6500 - 5000 = 1500$$ Step 3: Apply the Simple

The product of two numbers is 2160 and their GCD is 12. What is the sum of the numbers if one of them is 60?

The correct answer is A: 92. If one number is 60 and product is 2160, then other number = 2160 ÷ 60 = 36. Sum = 60 + 36 = 96. Wait, let me verify GCD(60, 36) = 12. Yes, 12 is correct. Sum = 96.

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Quantitative aptitude questions for competitive exams

221 Q 7 Topics Take Mock Test

Difficulty: All Easy Medium Hard 71–80 of 221

Topics in Quantitative Aptitude

All Numbers 499 HCF and LCM 150 Profit and Loss 102 Time and Work 101 Percentage 101 Simple Interest 50 Average 48

Q.71 Medium Numbers

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.

Test

Q.72 Medium Numbers

A's income is 25% more than B's. By what % is B's income less than A's?

A 20%

B 25%

C 15%

D 18%

Correct Answer: A. 20%

EXPLANATION

Let B's income = 100, A's = 125. B's is less by 25/125 × 100 = 20%.

Test

Q.73 Medium Numbers

A trader marks goods 40% above cost price and gives 10% discount. What's his profit%?

A 26%

B 30%

C 32%

D 36%

Correct Answer: A. 26%

EXPLANATION

Let CP = 100. MP = 140. SP = 140 × 0.9 = 126. Profit% = (126-100)/100 × 100 = 26%.

Test

Q.74 Medium Numbers

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.

Test

Q.75 Medium Numbers

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

Test

Q.76 Medium Numbers

A retailer marks goods 50% above cost price. He gives 20% discount on marked price. What is net profit percentage?

A 20%

B 25%

C 30%

D 35%

Correct Answer: A. 20%

EXPLANATION

Let CP = 100. MP = 150. SP = 150 × 0.8 = 120. Profit% = 20%

Test

Q.77 Medium Numbers

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

Test

Q.78 Medium Numbers

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

Test

Q.79 Medium Numbers

A's salary is 20% less than B's. B's salary is what percentage more than A's?

A 20%

B 25%

C 30%

D 33.33%

Correct Answer: B. 25%

EXPLANATION

If B = 100, A = 80. Increase needed = 20. Percentage = (20/80) × 100 = 25%

Test

Q.80 Medium Numbers

Two trains of lengths 150m and 250m are moving towards each other at speeds of 45 km/h and 35 km/h. How long will they take to completely pass each other?

A 18 seconds

B 20 seconds

C 24 seconds

D 30 seconds

Correct Answer: A. 18 seconds

EXPLANATION

Total length = 400m. Relative speed = 45 + 35 = 80 km/h = 80 × 5/18 = 22.22 m/s. Time = 400/22.22 ≈ 18 seconds

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