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Number System - Aptitude MCQ Questions and Solutions with Explanations

Number System MCQ Questions and answers with easy and logical explanations.Arithmetic Ability provides you all type of quantitative and competitive aptitude mcq questions on Number System with easy and logical explanations. Number System MCQ is important for exams like Banking exams,IBPS,SCC,CAT,XAT,MAT etc. Page-9 section-2

Each section contains 100 MCQs on Number System .
81
The unit digit in the product 771 × 663 × 365 = ?
Discuss
Answer & Solution
Answer: Option D
Solution:
    771   ×   663   ×   365
    ↓   ↓   ↓
Unit Place   73   63   31
    ↓   ↓   ↓
Unit Digit ⇒ 3   ×   6   ×   3 = 54
  ⇒ 4 is answer
82
If sum of the two number is 80 and ratio is 3 : 5, then find numbers :
Discuss
Answer & Solution
Answer: Option D
Solution:
Let number are a, b = 3x, 5x
So, 3x + 5x = 8x = 80
x = 10
So, number is :
3 × 10 = 30
5 × 10 = 50
83
$$\frac{2}{3}$$ of three-fourth of a number is :
Discuss
Answer & Solution
Answer: Option A
Solution:
$$\eqalign{ & = \frac{2}{3} \times \frac{3}{4} \times n\,\,\,\left( {{\text{n}}\,{\text{is}}\,{\text{a}}\,{\text{number}}} \right) \cr & = \frac{1}{2}n \cr} $$
84
The greatest four digit number which is exactly divisible by each one of the numbers 12, 18, 21 and 28 :
Discuss
Answer & Solution
Answer: Option A
Solution:
L.C.M of 12, 18, 21, 28 = 252
9999 is divided by 252
Then remainder is 171
= 9999 - 171
The number will be = 9828
85
A number exceeds its two fifth by 75. The number is :
Discuss
Answer & Solution
Answer: Option A
Solution:
Let the number = x
⇒ According to the question,
$$\eqalign{ & \Rightarrow x - \frac{2}{5}x = 75 \cr & \Rightarrow \frac{{5x - 2x}}{5} = 75 \cr & \Rightarrow 3x = 75 \times 5 \cr & \Rightarrow x = 125 \cr} $$
86
The smallest number, which should be added to 756896, so as to obtain a multiple of 11, is :
Discuss
Answer & Solution
Answer: Option C
Solution:
For divisibility of 11
= 756896
= (9 + 6 + 7) - (6 + 8 + 5)
= 3
So, 3 should be added to number to make it divisible by 11
87
If sum of two numbers be a and their product be b, then the sum of their reciprocals is :
Discuss
Answer & Solution
Answer: Option C
Solution:
Let the two number are P and Q
P + Q = a
PQ = b
⇒ $$\frac{{1}}{{P}}$$ + $$\frac{{1}}{{Q}}$$
⇒ $$\frac{{Q + P}}{{PQ}}$$
⇒ $$\frac{{a}}{{b}}$$
88
If the numbers $$ \root 3 \of {9} , \root 4 \of 20 , \root 6 \of {25} $$   are arranged in ascending order, then the right arrangement is -
Discuss
Answer & Solution
Answer: Option C
Solution:
$$\root 3 \of 9 ,\,\,\root 4 \of {20} ,\,\,\root 6 \of {25} $$
Taking L.C.M of 3, 4 and 6
$$\eqalign{ & = \root {12} \of {{9^4}} ,\,\,\root {12} \of {{{20}^3}} ,\,\,\root {12} \of {{{25}^2}} \cr & = \root {12} \of {6561} ,\,\,\root {12} \of {8000} ,\,\,\root {12} \of {625} \cr} $$
So, ascending order
$$ = \root 6 \of {25} , < \root 3 \of 9 , < \root 4 \of {20} $$
89
Which of the following fraction is the smallest ?
$$\frac{8}{{15}},$$ $$\frac{{14}}{{33}},$$ $$\frac{7}{{13}},$$ $$\frac{{11}}{{13}}$$
Discuss
Answer & Solution
Answer: Option B
Solution:
$$\frac{8}{{15}},\frac{{14}}{{33}},\frac{7}{{13}},\frac{{11}}{{13}}$$

(264) , (210)  
↑   ↑  
$$\frac{8}{{15}}$$   ⤩   $$\frac{14}{{33}}$$  = $$\frac{8}{{15}}$$ > $$\frac{14}{{33}}$$
(182) , (231)  
↑   ↑  
$$\frac{14}{{33}}$$   ⤩   $$\frac{7}{{13}}$$  = $$\frac{14}{{33}}$$ < $$\frac{7}{{13}}$$ < $$\frac{11}{{13}}$$

$${\text{So}}\frac{{14}}{{33}}\,{\text{is}}\,{\text{smallest}}$$
90
When 'n' is divisible by 5 the remainder is 2. What is the remainder when n2 is divided by 5 ?
Discuss
Answer & Solution
Answer: Option D
Solution:
$$\eqalign{ & \frac{{\text{n}}}{5} \Rightarrow {\text{remainder}}\,\,2 \cr & {\text{if we put n = 7}} \cr} $$
Then it satisfies above situation
$$\eqalign{ & {\text{so n = 7}} \cr & \frac{{{{\text{n}}^2}}}{5} = \frac{{{7^2}}}{5} = \frac{{49}}{5} \cr & \Rightarrow {\text{remainder = 4}} \cr} $$