6500+ Quantitative Aptitude Questions and Answers With Explanation

Q:

The average age of a group of 10 students is 15 years. When 5 more students join the group, the average age increase by 1 year. The average age of the new student is?

Answer

Total age of 10 students = 150 years

Total age of 15 students = 240 years

Total age of 5 new students = 240 - 150 = 90 years

$\therefore$ Average age of 5 new students = 90/5 = 18 years.

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Subject: Problems on Ages

5 6351

Q:

In an old Palace there are 50 stairs to go on top floor. Each is 20 cm high, 30 cm wide and 60 cm long. If all the stairs are re-plastered at the rate of Rs. 4 per 100 sq.cm. What is the expenditure ?

A) Rs. 4680	B) Rs. 7600
C) Rs. 6000	D) Rs. 5480

Answer & Explanation Answer: C) Rs. 6000

Explanation:

Total are of all stairs = 50 (20x60 + 30x60)

= 50 (1200 + 1800)

= 50 x 3000

= 150000 sq cm.

Given rate of 100 sq cm = Rs. 4

Then for 150000 sq. cm = ?

=> 4 x 150000/100 = Rs. 6000

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Filed Under: Area
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11 6350

Q:

The difference between 4632 and 20000 is what number

A) 15368	B) 12652
C) 14562	D) 14965

Answer & Explanation Answer: A) 15368

Explanation:

The difference between 4632 and 20000 is given by subtracting smaler number from the bigger number.

Here the bigger number is 20000

Smaller number is 4632

Now, subtracting 4632 from 20000

20000 - 4632 = 15368 and the resut is an even number.

Hence, The difference between 4632 and 20000 is 15368 and is an even number.

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Filed Under: Problems on Numbers
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0 6349

Q:

The ratio of the speeds of a car, a jeeps and a tractor is 3 : 5 : 2. The speed of the jeep is 250 per cent of the speed of the tractor and tractor covers 360 km in 12 hours. What is the average speed of car and jeep together?

A) 50 kmph	B) 60 kmph
C) 70 kmph	D) 80 kmph

Answer & Explanation Answer: B) 60 kmph

Explanation:

Speed of tractor = 360/12 = 30 kmph

Speed of jeep = 250 x 30/100 = 75 kmph

But, given ratio of speed of car, jeep and tractor is 3 : 5 : 2

Speed of car = 3 x 75/5 = 45 kmph

Required, average speed of car and jeep = 75 + 45/2 = 60 kmph.

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Filed Under: Time and Distance
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15 6341

Q:

A passenger train is moving at a speed of 120 km/hr. If the length of the train is 101 meters, how long will it take to cross a railway platform 154 meters long ?

A) 6.24 sec	B) 6.58 sec
C) 7.325 sec	D) 7.65 sec

Answer & Explanation Answer: D) 7.65 sec

Explanation:

Here total distance = 154 + 101 = 255 mts
Given speed = 120 kmph = 120x5/18 m/sec
Hence, Time = d/s = 255x18/120x5 = 7.65 sec

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Filed Under: Problems on Trains
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8 6340

Q:

Consider 5 independent Bernoulli’s trials each with probability of success p. If the probability of at least one failure is greater than or equal to 31/32 , then p lies in the interval ?

A) [1, 32]	B) (0, 1)
C) [1, 1/2]	D) (1, 1/2]

Answer & Explanation Answer: C) [1, 1/2]

Explanation:

Probability of atleast one failure
= 1 - no failure > 31/32
= 1 - $P^{5}$ > 31/32
= $P^{5} <$ 1/32
= p < 1/2
Also p > 0
Hence p lies in [0,1/2].

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Filed Under: Probability
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5 6331

Q:

When 52416 is divided by 312, the quotient is 168. what will be the quotient when 52.416 is divided by 0.0168?

A) 3.12	B) 312
C) 3120	D) None of these

Answer & Explanation Answer: C) 3120

Explanation:

Given, $\frac{52416}{312} = 168 \Leftrightarrow \frac{52416}{168} = 312$

Now , $\frac{52.416}{0.0168} = \frac{52416}{16.8} = \frac{52416}{168} \times 10 = 312 \times 10 = 3120$

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Filed Under: Decimal Fractions

9 6317

Q:

Ajay and his wife Reshmi appear in an interview for two vaccancies in the same post. The Probability of Ajay's selection is 1/7 and that of his wife Reshmi's selection is 1/5. What is the probability that only one of them will be selected?

A) 5/7	B) 1/5
C) 2/7	D) 2/35

Answer & Explanation Answer: C) 2/7

Explanation:

P( only one of them will be selected) = p[(E and not F) or (F and not E)]

= $P [(E \cap F) \cup (F \cap E)]$

= $P (E) P (F) + P (F) P (E)$

= $\frac{1}{7} \times \frac{4}{5} + \frac{1}{5} \times \frac{6}{7} = \frac{2}{7}$

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Filed Under: Probability
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17 6312

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