6500+ Quantitative Aptitude Questions and Answers With Explanation

Q:

If x is chosen at random from the set {1,2,3,4} and y is to be chosen at random from the set {5,6,7}, what is the probability that xy will be even?

A) 1/2	B) 2/3
C) 3/4	D) 4/3

Answer & Explanation Answer: B) 2/3

Explanation:

S ={(1,5),(1,6),(1,7),(2,5),(2,6),(2,7),(3,5),(3,6),(3,7),(4,5),(4,6),(4,7)}
Total element n(S)=12

xy will be even when even x or y or both will be even.
Events of x, y being even is E.
E ={(1,6),(2,5),(2,6),(2,7),(3,6),(4,5),(4,6),(4,7)}
n(E) = 8

P(E)=n(E)n(S)=812 = 4/3

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Filed Under: Probability

15 9976

Q:

An amount doubles itself in 15 years. what is the rate of interest ?

A) 7.85 %	B) 9.41%
C) 6.66 %	D) 4.21 %

Answer & Explanation Answer: C) 6.66 %

Explanation:

Let the principle be Rs. P
As the amount double itself the interest is Rs. P too
So P = P x r x 15/100
=> r = 100/15 = 20/3 % = 6.66 %.

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Filed Under: Simple Interest
Exam Prep: AIEEE , Bank Exams , CAT , GATE , GRE
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5 9974

Q:

A train is traveling at 48 kmph . It crosses another train having half of its length , traveling in opposite direction at 42 kmph, in 12 seconds. It also passes a railway platform in 45 seconds. What is the length of the platform ?

A) 500	B) 400
C) 360	D) 480

Answer & Explanation Answer: B) 400

Explanation:

Speed of train 1 = 48 kmph
Let the length of train 1 = 2x meter

Speed of train 2 = 42 kmph
Length of train 2 = x meter (because it is half of train 1's length)

Distance = 2x + x = 3x
Relative speed= 48+42 = 90 kmph = (90*5/18) m/s = 25 m/s

Time = 12 s

Distance/time = speed

=>3x/12 = 25 $\Rightarrow$ (25*12)/3

Length of the first train = 2x = 200 meter
Time taken to cross the platform= 45 s

Speed of train 1 = 48 kmph = 480/36 = 40/3 m/s

Distance = 200 + y [where y is the length of the platform]

x =100m => 200+y = 45* 40/3
$\Rightarrow$ y = 400m

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Filed Under: Problems on Trains

13 9958

Q:

A rectangular field is to be fenced on three sides leaving a side of 20 feet uncovered. If the area of the field is 680 sq. feet, how many feet of fencing will be required?

A) 22	B) 44
C) 66	D) 88

Answer & Explanation Answer: D) 88

Explanation:

We have: l = 20 ft and lb = 680 sq. ft.So, b = 34 ft.

Length of fencing = (l + 2b) = (20 + 68) ft = 88 ft.

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Filed Under: Area
Exam Prep: Bank Exams
Job Role: Bank PO

3 9958

Q:

A train 800 metres long is running at a speed of 78 km/hr. If it crosses a tunnel in 1 minute, then the length of the tunnel (in meters) is :

A) 130	B) 360
C) 500	D) 540

Answer & Explanation Answer: C) 500

Explanation:

Speed =[ 78 x ( 5/18 ) ] m/sec = 65/3 m/sec.

Time = 1 minute = 60 sec.

Let the length of the tunnel be x metres.

Then, [ (800 + x )/ 60 ]= 65/3

$\Rightarrow$ 3(800 + x) = 3900

$\Rightarrow$ x = 500.

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Filed Under: Problems on Trains

12 9921

Q:

At present, the ratio between the ages of Arun and Harish is 4:3. After 6 years, Arun's age will be 26 years. What is the age of Harish at present ?

A) 15 years	B) 16 years
C) 18 years	D) 21 years

Answer & Explanation Answer: A) 15 years

Explanation:

Let the present ages of Arun and Harish be 4x and 3x years respectively.

Then, 4x + 6 = 26 => x = 5

Harish's age = 3x = 15 years.

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Filed Under: Problems on Ages
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8 9910

Q:

A trader sold an article at profit of 20%. Had he bought that article at 60% less price and sold it at Rs 90 less, then he would have gained 50%. What is the value (in Rs) of cost price?