6500+ Quantitative Aptitude Questions and Answers With Explanation

Q:

The number of ways that 8 beads of different colours be strung as a necklace is

A) 2520	B) 2880
C) 4320	D) 5040

Answer & Explanation Answer: A) 2520

Explanation:

The number of ways of arranging n beads in a necklace is $\frac{(n - 1)!}{2} = \frac{(8 - 1)!}{2} = \frac{7!}{2}$ = 2520

(since n = 8)

Report Error

View Answer Report Error Discuss

Filed Under: Permutations and Combinations
Exam Prep: AIEEE , Bank Exams , CAT
Job Role: Bank Clerk , Bank PO

27 16638

Q:

Two trains having equal lengths, take 10 seconds and 15 seconds respectively to cross a post. If the length of each train is 120 meters, in what time (in seconds) will they cross each other when traveling in opposite direction?

A) 10	B) 25
C) 12	D) 20

Answer & Explanation Answer: C) 12

Explanation:

Speed of train 1 = $(\frac{120}{10}) m / s e c$ = 12 m/sec

Speed of train 2 = $(\frac{120}{15}) m / s e c$ = 8 m/sec

if they travel in opposite direction, relative speed = 12 + 8 = 20 m/sec

distance covered = 120 + 120 = 240 m

time = distance/speed = 240/20 = 12 sec

Report Error

View Answer Report Error Discuss

Filed Under: Problems on Trains

22 16636

Q:

How many cubes of 10cm edge can be put in a cubical box of 1m edge

A) 10	B) 100
C) 1000	D) 10000

Answer & Explanation Answer: C) 1000

Explanation:

Number of cubes= (100x100x100) / (10x10x10)= 1000

Report Error

View Answer Report Error Discuss

Filed Under: Volume and Surface Area
Exam Prep: Bank Exams
Job Role: Bank PO

45 16621

Q:

A box contains 100 balls, numbered from 1 to 100. If three balls are selected at random and with replacement from the box, what is the probability that the sum of the three numbers on the balls selected from the box will be odd?

A) 1/6	B) 1/3
C) 1/2	D) 1/4

Answer & Explanation Answer: C) 1/2

Explanation:

P(odd) = P (even) = $\frac{1}{2}$ 1(because there are 50 odd and 50 even numbers)

Sum or the three numbers can be odd only under the following 4 scenarios:

Odd + Odd + Odd = $\frac{1}{2} * \frac{1}{2} * \frac{1}{2}$ = $\frac{1}{8}$

Odd + Even + Even = $\frac{1}{2} * \frac{1}{2} * \frac{1}{2}$ = $\frac{1}{8}$

Even + Odd + Even = $\frac{1}{2} * \frac{1}{2} * \frac{1}{2}$ = $\frac{1}{8}$

Even + Even + Odd = $\frac{1}{2} * \frac{1}{2} * \frac{1}{2}$ = $\frac{1}{8}$

Other combinations of odd and even will give even numbers.

Adding up the 4 scenarios above:

= $\frac{1}{8}$ + $\frac{1}{8}$ + $\frac{1}{8}$ + $\frac{1}{8}$ = $\frac{4}{8}$ = $\frac{1}{2}$

Report Error

View Answer Report Error Discuss

Filed Under: Probability

10 16595

Q:

The third proportional to $(x^{2} - y^{2})$ and $(x - y)$ is :

A) (x + y )	B) (x - y)
C) (x + y) / ( x - y)	D) (x -y) / ( x + y)

Answer & Explanation Answer: D) (x -y) / ( x + y)

Explanation:

Let the third proportional to $(x^{2} - y^{2})$ and $(x - y)$ be z. Then,

$(x^{2} - y^{2}) : (x - y) : : (x - y) : z$

$= > (x^{2} - y^{2}) * z = {(x - y)}^{2}$

=> z= $\frac{{(x - y)}^{2}}{(x^{2} - y^{2})} = \frac{(x - y)}{(x + y)}$

Report Error

View Answer Report Error Discuss

Filed Under: Ratios and Proportions

65 16586

Q:

The average age of a group of persons going for picnic is 16 years. Twenty new persons with an average age of 15 years join the group on the spot due to which their average age becomes 15.5 years. The number of persons initially going for picnic is :

A) 15	B) 20
C) 23	D) 24

Answer & Explanation Answer: B) 20

Explanation:

Let the initial number of persons be x. Then,

16x + 20 * 15 = 15.5 (x + 20) <=> 0.5x = 10 <=> x = 20.

Report Error

View Answer Report Error Discuss

Filed Under: Average

19 16581

Q:

In a 48 ltr mixture, the ratio of milk and water is 5:3. How much water should be added in the mixture so as the ratio will become 3:5 ?

A) 24 lit	B) 16 lit
C) 32 lit	D) 8 lit

Answer & Explanation Answer: C) 32 lit

Explanation:

Given mixture = 48 lit

Milk in it = 48 x 5/8 = 30 lit

=> Water in it = 48 - 30 = 18 lit

Let 'L' lit of water is added to make the ratio as 3:5

=> 30/(18+L) = 3/5

=> 150 = 54 + 3L

=> L = 32 lit.

Report Error

View Answer Report Error Discuss

Filed Under: Alligation or Mixture
Exam Prep: AIEEE , Bank Exams , CAT , GATE
Job Role: Bank Clerk , Bank PO

36 16575

Q:

A man’s current age is $\frac{2}{5}$ of the age of his father. After 8 years, he will be $\frac{1}{2}$ of the age of his father. What is the age of father at now ?

A) 50	B) 40
C) 33	D) 30

Answer & Explanation Answer: B) 40

Explanation:

Let, father’s current age is A years.
Then, Man’s current age = $[(\frac{2}{5} * A)]$ years.

$[(\frac{2}{5} * A)]$ +8= $(\frac{1}{2}) (A + 8)$

2(2A+40) = 5(A+8)

A = 40

Report Error

View Answer Report Error Discuss

Filed Under: Problems on Ages

23 16556

Quantitative Aptitude - Arithmetic Ability Questions

Quick Links