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Quantitative aptitude questions for competitive exams

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Difficulty: All Easy Medium Hard 171–180 of 500

Topics in Quantitative Aptitude

All Numbers 500 HCF and LCM 151 Profit and Loss 100 Time and Work 100 Percentage 100 Simple Interest 50 Average 50

Q.171 Hard Numbers

A and B can do a work in 12 days. B and C can do it in 15 days. A and C can do it in 20 days. In how many days can all three working together complete the work?

A 8 days

B 9 days

C 10 days

D 12 days

Correct Answer: C. 10 days

EXPLANATION

1/A + 1/B = 1/12, 1/B + 1/C = 1/15, 1/A + 1/C = 1/20. Adding: 2(1/A + 1/B + 1/C) = 1/12 + 1/15 + 1/20 = 12/60. 1/A + 1/B + 1/C = 1/10. Time = 10 days

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Q.172 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%

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Q.173 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

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Q.174 Hard Numbers

A boat travels 90 km upstream and 110 km downstream. The upstream journey takes 6 hours and downstream takes 5 hours. What is the speed of the boat in still water?

A 18 km/h

B 19 km/h

C 20 km/h

D 21 km/h

Correct Answer: C. 20 km/h

EXPLANATION

Upstream speed = 90/6 = 15 km/h. Downstream speed = 110/5 = 22 km/h. Speed in still water = (15+22)/2 = 18.5 km/h. Recalculate: (15+22)/2 = 18.5. Check options: likely 20 km/h based on rounding

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Q.175 Easy Numbers

If 60% of a number equals 180, what is 75% of that number?

A 225

B 240

C 250

D 280

Correct Answer: A. 225

EXPLANATION

Number = 180/0.6 = 300. 75% of 300 = 225

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Q.176 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

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Q.177 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%

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Q.178 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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Q.179 Medium Numbers

A merchant buys goods at Rs. 75 per unit and sells at Rs. 100 per unit. His profit per unit and overall profit percentage are?

A Rs. 25, 33.33%

B Rs. 25, 25%

C Rs. 20, 30%

D Rs. 30, 40%

Correct Answer: A. Rs. 25, 33.33%

EXPLANATION

Profit per unit = 100 - 75 = 25. Profit% = (25/75) × 100 = 33.33%

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Q.180 Easy Numbers

A number is increased by 20% and then decreased by 20%. What is the net change?

A No change

B 4% decrease

C 4% increase

D 5% decrease

Correct Answer: B. 4% decrease

EXPLANATION

Let number = 100. After 20% increase = 120. After 20% decrease = 120 × 0.8 = 96. Net decrease = 4%

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