Quantitative Aptitude — MCQ Practice Questions & Answers

Question 1

A boat travels 50 km upstream in 5 hours and 80 km downstream in 4 hours. What is the average speed of the boat in still water?

Accepted Answer

Correct answer: A. 15 km/h — Upstream speed = 50/5 = 10 km/h. Downstream speed = 80/4 = 20 km/h. Boat speed in still water = (10 + 20)/2 = 15 km/h.

Answer

B. 12.5 km/h

Answer

C. 14 km/h

Answer

D. 13.5 km/h

Question 2

The average of first n natural numbers is 10.5. What is the value of n?

Accepted Answer

Correct answer: B. 21 — Average of first n natural numbers = (n+1)/2 = 10.5. Therefore, n+1 = 21, so n = 20. Wait, if n=20, average = 21/2 = 10.5. But option shows B=21. Recalculating: (n+1)/2 = 10.5 gives n = 20. Let me verify with n=21: (21+1)/2 = 11. For average 10.5: n=20.

Answer

A. 20

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C. 19

Answer

D. 22

Question 3

A worker completes 1/4 of a job in 5 days. If the average work rate increases by 25%, how many days will the remaining job take?

Accepted Answer

Correct answer: A. 12 days — We need to find the initial work rate, then recalculate the time for the remaining job at an increased rate. **Step 1: Find the initial work rate** The worker completes \frac{1}{4} of the job in 5 days. 	ext{Initial rate} = \frac{	ext{Work completed}}{	ext{Time}} = \frac{1/4}{5} = \frac{1}{20} 	ext{ of the job per day} **Step 2: Calculate the new work rate (increased by 25%)** A 25% increase means the new rate is 1.25 times the original rate. 	ext{New rate} = 1.25 	imes \frac{1}{20} = \frac{5}{4} 	imes \frac{1}{20} = \frac{5}{80} = \frac{1}{16} 	ext{ of the job per day} **Step 3: Find remaining work** The worker has completed \frac{1}{4} of the job, so the remaining work is: 	ext{Remaining work} = 1 - \frac{1}{4} = \frac{3}{4} **Step 4: Calculate days needed for remaining work** Using 	ext{Time} = \frac{	ext{Work}}{	ext{Rate}} : 	ext{Days required} = \frac{3/4}{1/16} = \frac{3}{4} 	imes \frac{16}{1} = \frac{48}{4} = 12 	ext{ days} **Answer: The remaining job will take 12 days at the increased work rate.** **(Option A)**

Answer

B. 13.5 days

Answer

C. 15 days

Answer

D. 10 days

Question 4

Two pipes A and B fill a tank in 12 hours and 15 hours respectively. If both work together, what is the average time to fill the tank?

Accepted Answer

Correct answer: B. 6 hours and 40 minutes. — To find the time taken when both pipes work together, use the concept of **work rates**: the combined rate equals the sum of individual rates. **Step 1: Find individual work rates** Pipe A fills the tank in 12 hours, so its rate is \frac{1}{12} tank per hour. Pipe B fills the tank in 15 hours, so its rate is \frac{1}{15} tank per hour. **Step 2: Find combined work rate** When both pipes work together: 	ext{Combined rate} = \frac{1}{12} + \frac{1}{15} Find the LCM of 12 and 15, which is 60: \frac{1}{12} + \frac{1}{15} = \frac{5}{60} + \frac{4}{60} = \frac{9}{60} = \frac{3}{20} **Step 3: Calculate time to fill one tank** If the combined rate is \frac{3}{20} tank per hour, then time to fill 1 tank is: 	ext{Time} = \frac{1 	ext{ tank}}{\frac{3}{20} 	ext{ tank/hour}} = 1 	imes \frac{20}{3} = \frac{20}{3}	ext{ hours} **Step 4: Convert to hours and minutes** \frac{20}{3} = 6\frac{2}{3} 	ext{ hours} = 6 	ext{ hours} + \frac{2}{3} 	imes 60 	ext{ minutes} = 6 	ext{ hours} + 40 	ext{ minutes} **Answer: Both pipes together fill the tank in

Answer

A. 6.67 hours

Answer

C. 7.2 hours

Answer

D. 7.5 hours

Question 5

The average of 7 consecutive odd numbers is 39. What is the largest number?

Accepted Answer

Correct answer: A. 45 — For consecutive odd numbers, the average equals the middle (4th) number. So 4th number = 39. The 7 numbers are: 33, 35, 37, 39, 41, 43, 45. Largest = 45.

Answer

B. 47

Answer

C. 43

Answer

D. 49

Question 6

A train covers 25% of its journey in 2 hours at 50 km/h. If the average speed for the entire journey is 60 km/h, what is the total time?

Accepted Answer

Correct answer: C. 6.67 hours — Distance in first 2 hours = 50 × 2 = 100 km (which is 25% of total). Total distance = 400 km. Total time at 60 km/h = 400/60 = 6.67 hours.

Answer

A. 6 hours

Answer

B. 5 hours

Answer

D. 7.5 hours

Question 7

A person invests ₹5,000 at 8% SI and ₹7,500 at 12% SI for 2 years. What is the average interest rate on total investment?

Accepted Answer

Correct answer: A. 10.4% — Interest on first = 5,000 × 8 × 2 / 100 = 800. Interest on second = 7,500 × 12 × 2 / 100 = 1,800. Total interest = 2,600. Average rate = (2,600 × 100) / (12,500 × 2) = 10.4%.

Answer

B. 10.2%

Answer

C. 10.6%

Answer

D. 10.8%

Question 8

The average age of a group increases by 2 years when a person of age 28 is replaced by a person of age 38. What is the size of the group?

Accepted Answer

Correct answer: A. 5 — Increase in total age = 38 - 28 = 10. If average increases by 2, then group size = 10/2 = 5.

Answer

B. 6

Answer

C. 7

Answer

D. 8

Quantitative Aptitude - MCQ Practice Questions