Aptitude - Problems on Numbers

Why Aptitude Problems on Numbers?

In this section you can learn and practice Aptitude Questions based on "Problems on Numbers" and improve your skills in order to face the interview, competitive examination and various entrance test (CAT, GATE, GRE, MAT, Bank Exam, Railway Exam etc.) with full confidence.

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How to solve Aptitude Problems on Numbers problems?

You can easily solve all kind of Aptitude questions based on Problems on Numbers by practicing the objective type exercises given below, also get shortcut methods to solve Aptitude Problems on Numbers problems.

Exercise :: Problems on Numbers - General Questions

1. 

If one-third of one-fourth of a number is 15, then three-tenth of that number is:

A. 35
B. 36
C. 45
D. 54

Answer: Option D

Explanation:

Let the number be x.

Then, 1 of 1 of x = 15      x = 15 x 12 = 180.
3 4

So, required number = 3 x 180 = 54.
10


2. 

Three times the first of three consecutive odd integers is 3 more than twice the third. The third integer is:

A. 9
B. 11
C. 13
D. 15

Answer: Option D

Explanation:

Let the three integers be x, x + 2 and x + 4.

Then, 3x = 2(x + 4) + 3      x = 11.

Third integer = x + 4 = 15.


3. 

The difference between a two-digit number and the number obtained by interchanging the positions of its digits is 36. What is the difference between the two digits of that number?

A. 3
B. 4
C. 9
D. Cannot be determined
E. None of these

Answer: Option B

Explanation:

Let the ten's digit be x and unit's digit be y.

Then, (10x + y) - (10y + x) = 36

9(x - y) = 36

x - y = 4.


4. 

The difference between a two-digit number and the number obtained by interchanging the digits is 36. What is the difference between the sum and the difference of the digits of the number if the ratio between the digits of the number is 1 : 2 ?

A. 4
B. 8
C. 16
D. None of these

Answer: Option B

Explanation:

Since the number is greater than the number obtained on reversing the digits, so the ten's digit is greater than the unit's digit.

Let ten's and unit's digits be 2x and x respectively.

Then, (10 x 2x + x) - (10x + 2x) = 36

9x = 36

x = 4.

Required difference = (2x + x) - (2x - x) = 2x = 8.


5. 

A two-digit number is such that the product of the digits is 8. When 18 is added to the number, then the digits are reversed. The number is:

A. 18
B. 24
C. 42
D. 81

Answer: Option B

Explanation:

Let the ten's and unit digit be x and 8 respectively.
x

Then, 10x + 8 + 18 = 10 x 8 + x
x x

10x2 + 8 + 18x = 80 + x2

9x2 + 18x - 72 = 0

x2 + 2x - 8 = 0

(x + 4)(x - 2) = 0

x = 2.