Practice MCQ Questions and Answer on Number System

641.

What decimal of a week is an hour?

(A) .0059
(B) .0062
(C) .062
(D) .059

Solution: $\frac{1}{24 \times 7} = 0.0059$

642.

A man sells chocolates which are in the boxes. Only either full box or half a box of chocolates can be purchased from him. A customer comes and buys half the number of boxes which the seller had plus half box more. A second customer comes and purchases half the remaining number of boxes plus half a box. After this the seller is left with no chocolate boxes. How many chocolate boxes the seller had initially?

(A) 2
(B) 3
(C) 4
(D) 3.5

Solution: The best way to go through the options Let there are initially 3 boxes then, 1st customer gets = $\frac{3}{2}$ + $\frac{1}{2}$ = 2 Remaining boxes = 3 - 2 = 1 2nd customer = $\frac{1}{2}$ + $\frac{1}{2}$ = 1 So, option B is correct.

643.

The real number to be added to 13851 to get a number which is divisible by 87 is:

(A) 18
(B) 43
(C) 54
(D) 69

644.

The numerator and denominator of a fraction are in the ratio 3 : 4. If 9 is subtracted from the numerator, the resulting fraction in $\frac{2}{3}$ of the original fraction. The numerator of the original fraction is

(A) 27
(B) 18
(C) 36
(D) 9

Solution: $\begin{aligned} Let the fraction be \frac{3 k}{4 k} \\ ∴ \frac{3 k - 9}{4 k} = \frac{2}{3} \\ ∴ 9 k - 27 = 8 k \\ ∴ k = 27 \end{aligned}$

645.

A number of boys raised Rs. 400 for a famine relief fund, each boy giving as many 25 paise coins as there were boys. The number of boys was -

(A) 40
(B) 16
(C) 20
(D) 100

Solution: $\begin{aligned} Let number of boys = x \\ Number of 25 paise coins = x^{2} \\ According to question, \\ \frac{x^{2}}{4} = 400 \\ x^{2} = 1600 \\ x = 40 \end{aligned}$

646.

If m and n are natural numbers such that 2^m - 2ⁿ = 960, what is the value of m ?

(A) 10
(B) 12
(C) 15
(D) Cannot be determined

647.

Which one of the following is a factor of the sum of first twenty-five natural numbers ?

(A) 26
(B) 24
(C) 13
(D) 12

Solution: Sum first n natural numbers $= [\frac{n(n + 1)}{2}] = 25 \times 13$ Sum of first 25 natural numbers $= \frac{25 (26)}{2} = 25 \times 13$ Now check option Clearly, we can see 13 is factor So, '13' is answer

648.

In a class of students, the first student has 2 toffees, second has 4 toffees. third has 6 toffees and so on. If the number of students in the class is 25. Then the total number of toffees are divisible by . . . . . .

(A) 5 and 7
(B) 5 and 13
(C) 11 and 13
(D) 7 and 11

Solution: $\begin{aligned} 2 + 4 + 6 + . . . . . . \\ S_{n} = \frac{n}{2} [2 a + (n - 1) d] \\ = \frac{25}{2} [2 \times 2 + 24 \times 2] \\ = \frac{25}{2} \times 52 \\ = 25 \times 26 \\ Clearly it is divisible by 5, 13 \end{aligned}$

649.

The value of (1018) - 1019 ÃÂÃÂÃÂÃÂÃÂÃÂ 1017 + 1015 ÃÂÃÂÃÂÃÂÃÂÃÂ 1012 - 1016 ÃÂÃÂÃÂÃÂÃÂÃÂ 1011 is:2

(A) 1
(B) 4
(C) 3
(D) 5

650.

How many number between 1000 and 5000 are exactly divisible by 225 ?

(A) 16
(B) 18
(C) 19
(D) 12

Solution: $\begin{aligned} First number = 1125 \\ Last number = 4950 \\ Number of term \\ = \frac{4950 - 1125}{225} + 1 \\ = \frac{3825}{225} + 1 \\ = 17 + 1 \\ = 18 \end{aligned}$

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Practice MCQ Questions and Answer on Number System

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