Practice MCQ Questions and Answer on Number System

11.

(91 + 92 + 93 + . . . . . . + 110) is equal to

(A) 4020
(B) 2010
(C) 6030
(D) 8040

Solution: $\begin{aligned} 1 + 2 + 3 + . . . . . . + n = \frac{n (n + 1)}{2} \\ ∴ 91 + 92 + . . . . . . + 110 \\ = (1 + 2 + . . . . . . + 110) - (1 + 2 + . . . . . . + 90) \\ = \frac{110 \times 111}{2} - \frac{90 \times 91}{2} \\ = 6105 - 4095 \\ = 2010 \end{aligned}$

12.

What number multiplied by 48 will give the same product as 173 multiplied by 240 ?

(A) 495
(B) 545
(C) 685
(D) 865

Solution: Let x × 48 = 173 × 240Then, x = $\frac{173 \times 240}{48}$ x = 173 × 5 x = 865

13.

The sum of 10 terms of the arithmetic series is 390. If the third term of the series is 19. Find the first term?

(A) 3
(B) 5
(C) 7
(D) 8

Solution: $\begin{aligned} Sum of A .P . = \frac{n}{2} [2 a + (n - 1) d] \\ n^{th} term = a + (n - 1) d \\ 3^{rd} term = a + (3 - 1) d = 19 \\ a + 2 d = 19 . . . . . . (i) \\ Sum of 10 term = \frac{10}{2} [2 a + 9 d] = 390 \\ 2 a + 9 d = 78 . . . . . . (ii) \\ a + 2 d = 19 . . . . . . (i) \\ From equation (i) and (ii) \\ a = 3 d = 8 \end{aligned}$

14.

5566 - 7788 + 9988 = ? + 4444

(A) 3223
(B) 3232
(C) 3322
(D) 3333

15.

For the integer n, if n³ is odd, then which of the following statements are true ?
I. n is odd
II. n² is odd
III. n² is even

(A) I only
(B) II only
(C) I and II only
(D) I and III only

16.

If x and y are two digits of the number 653xy such that the number is divisible by 80, then x + y is equal to :

(A) 3
(B) 4
(C) 5
(D) 6

17.

Which of following can never be ending of a perfect square?

(A) 00
(B) 000
(C) 1
(D) 6

18.

The least number that must be subtracted from 63520 to make the result a perfect square is -

(A) 30
(B) 24
(C) 14
(D) 16

19.

Find the value of $\frac{1}{5} +$ ÃÂÃÂ $999 \frac{494}{495} \times 99$ ÃÂÃÂ = ?

(A) 90000
(B) 99000
(C) 90900
(D) 99990

Solution: $\begin{aligned} \Leftrightarrow \frac{1}{5} + 999 \frac{494}{495} \times 99 \\ \Rightarrow \frac{1}{5} + [999 + \frac{494}{495}] \times 99 \\ \Rightarrow \frac{1}{5} + [999 + 1 - \frac{1}{495}] \times 99 \\ \Rightarrow \frac{1}{5} + [1000 - \frac{1}{495}] \times 99 \\ \Rightarrow \frac{1}{5} + 99000 - \frac{1}{5} \\ \Rightarrow 99000 \end{aligned}$

20.

A four-digit pin, say 'abcd', of a lock has different non-zero digits. The digits satisfy b = 2a, c = 2b, d = 2c. The pin is divisible by . . . . . . . .

(A) 2, 3, 5
(B) 2, 3, 7
(C) 2, 3, 13
(D) 2, 3, 11

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Practice MCQ Questions and Answer on Number System

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