Chapter 1: Number System

Solution:-

(D) LLX

As we know that, the symbol L can never be repeated.

Therefore, LLX is incorrect.

Solution:-

(C) 99987

In the given, options there are three numbers used 9, 8 and 7

To get the largest of 5- digit we have to arrange the numbers in descending order.

Then, from the given options 99987 is the largest of 5 – digit number.

Solution:-

In the given, options there are three numbers used 0, 1 and 2

To get the largest of 4- digit we have to arrange the numbers in ascending order.

Then, from the given options 1002 is the smallest of 4 – digit number.

Solution:-

(c) 29

Number of whole numbers between 38 and 68 is 29.

Solution:-

(B) 998000

The number which comes immediately before a particular number is called its predecessor.

The successor of a whole number is the number obtained by adding 1 to it.

So, Successor of 999 = 999 + 1 = 1000

Predecessor = 999 – 1 = 998

Then, product of successor and predecessor of 999 is = 1000 × 998

= 998000

Solution:-

(A) an even number

The product of a non-zero whole number and its successor is always an even number.

For example: – 4 × 5 = 20, 7 × 8 = 56

Solution:-

(C) 50

Let us assume the number be x.

From the question it is given that, number is added to 25 = x + 25

The same number is subtracted to from 25 = 25 – x

Then, the sum of the resulting numbers is = (x + 25) + (25 – x)

= x + 25 + 25 – x

= 50 + x – x

= 50 + 0

= 50

Solution:-

(C) 7 + 8 × 9 = (7 + 8) × (7 + 9)

Consider the left hand side = 7 + 8 × 9

= 7 + (8 × 9)

= 7 + 72

= 79

Now, consider the right hand side = (7 + 8) × (7 + 9)

= 15 × 16

= 240

By comparing LHS and RHS

LHS ≠ RHS

79 ≠ 240

Solution:-

(B) 10

Solution:-

(B) Zero is the identity for multiplication of whole numbers.

Example:- 1 × 0 = 0