**Number System Questions for RRB Group-D Set-3 PDF**

Download Top-10 RRB Group-D Number System Questions set – 3 PDF. RRB GROUP-D Maths questions based on asked questions in previous exam papers very important for the Railway Group-D exam.

Download Number System Questions for RRB Group-D Set-3 PDF

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**Question 1: **Sum of two positive integers is 15 and product of them is 50. What will be the L.C.M. of the numbers?

a) 50

b) 30

c) 40

d) 10

**Question 2: **If the product of the two numbers is 525 and L.C.M. of the numbers is 105, what will be the H.C.F. of the numbers?

a) 3

b) 4

c) 5

d) 6

**Question 3: **14 is the HCF of two numbers ‘p’ and ‘q’, where 14 < p < q. What is the minimum values of (p,q)?

a) 42, 28

b) 28, 14

c) 14, 28

d) 28, 42

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**Question 4: **Find the greatest number that divides 82, 147 and 199 so as to leave the same remainder in each case.

a) 7

b) 11

c) 13

d) 17

**Question 5: **Find the largest 4 digit number that is divisible by 78.

a) 9996

b) 9988

c) 9976

d) 9984

**Question 6: **Find the remainder when $79^{79}+79$ is divided by 80.

a) 78

b) 1

c) 79

d) 2

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**Question 7: **The product of two numbers is 7920 and their HCF is 12. Find the number of pairs of such numbers possible.

a) 1

b) 2

c) 3

d) 4

**Question 8: **The sum of first 50 natural numbers is:

a) 1225

b) 1250

c) 1300

d) 1275

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**Question 9: **The largest 5 digit number divisible by 99 is

a) 99999

b) 99990

c) 99991

d) 99980

**Question 10: **How many numbers between 1 and 1000 is divisible by 9?

a) 111

b) 110

c) 108

d) 114

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**Answers & Solutions:**

**1) Answer (D)**

Let’s say one of the number is x, hence another number will be 15-x

Hence, their product will be = $15x – x^2 = 50$

So after solving the above equation, we will get numbers as 10 and 5 and their L.C.M. will be 10

**2) Answer (C)**

As we know that the product of the two numbers = (L.C.M. of the numbers)*(H.C.F. of the numbers)

Hence, 525 = 105*(H.C.F.)

H.C.F. = 5

**3) Answer (D)**

Let the two numbers be 14x and 14y, where x and y are co-prime.

x, y > 1. The least possible values of x and y are 2 and 3 respectively.

So, the value of p is 14*2 = 28 and the value of q is 14*3 = 42

**4) Answer (C)**

147 – 82 = 65

199 – 147 = 52

The HCF of these differences is the number that divides all the three numbers leaving the same remainder.

65 = 13 * 5

52 = 13 * 4

=> HCF = 13

Hence, 13 is the answer.

**5) Answer (D)**

78*10 = 780

78 * 3 = 234

On adding the above, we get 78 * 13 = 1014

=> 78 * 130 = 10140

78 * 2 = 156

On subtracting the above, we get 78 * 128 = 9984

=> 9984 is the answer.

**6) Answer (A)**

($79^{79}+79$ mod 80) can be written as ($(-1)^{79}+79$ mod 80)

= (-1 + 79) mod 80

= 78 mod 80

= 78

**7) Answer (B)**

Let the two numbers be 12x and 12y

12x*12y = 7920

xy = 55 = 5*11 = 55*1

The two numbers can be [(12*5),(12*11)],[(12*55),(12*1)]

**8) Answer (D)**

Sum of first n natural numbers = n(n+1)/2

Sum of first 50 natural numbers = 50*51/2 = 1275

**9) Answer (B)**

Largest 5 digit number is 99999. This number on division by 99 gives 9 as a remainder.

The largest 5 digit number is 99999-9 = 99990

**10) Answer (A)**

Smallest number divisible by 9 in the given range is 9

Largest number in the given range is 999 which is divisible by 9.

The series goes like this:9, 18, 27, 36, 45……,999

999 = 9+(n-1)9

9(n-1) = 999-9 = 990

n-1 = 110

n = 111

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We hope this Number System Questions set – 3 PDF for RRB Group-D Exam will be highly useful for your preparation.