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Chapter 3

Integers — Mental Maths

Class - 6 RS Aggarwal Mathematics Solutions



Exercise 3(C) — Mental Maths

Question 1

Fill in the blanks :

(i) -36 + 8 = ...............

(ii) -36 - 8 = ...............

(iii) -46 - (-6) = ...............

(iv) 53 - (-10) = ...............

(v) 0 - (-13) = ...............

(vi) 9 + 1 - 61 = ...............

Answer

(i) -36 + 8 = -28.

(ii) -36 - 8 = -44.

(iii) -46 - (-6) = -40.

(iv) 53 - (-10) = 63.

(v) 0 - (-13) = 13.

(vi) 9 + 1 - 61 = -51.

Question 2(i)

Write T for true and F for false statement :

0 is a positive integer.

Answer

False

Reason

The number 0 is an integer, but it is neither positive nor negative.

Positive integers are numbers greater than 0 (1, 2, 3, ...).

Negative integers are numbers less than 0 (-1, -2, -3, ...).

Zero (0) is the integer that separates the positive and negative integers.

Question 2(ii)

Write T for true and F for false statement :

10°C below freezing point can be expressed as (-10°C).

Answer

True

Reason

The freezing point of water is 0°C. "10°C below freezing point" means 10 degrees less than 0°C, which is expressed as −10°C.

Question 2(iii)

Write T for true and F for false statement :

-(-15) = + 15

Answer

True

Reason

The negative of a negative number is a positive number. Therefore, −(−15) is equal to +15.

Question 2(iv)

Write T for true and F for false statement :

Predecessor of (- 9) is - 10.

Answer

True

Reason

The predecessor of a number is the number immediately before it.

Predecessor of (−9) = −9 − 1 = −10.

Question 2(v)

Write T for true and F for false statement :

On subtracting - 40 from 40, we get 80

Answer

True

Reason

The expression "subtracting -40 from 40" can be written as:

⇒ 40 − (−40)

⇒ 40 + 40

⇒ 80

Question 2(vi)

Write T for true and F for false statement :

Successor of -1 is 0.

Answer

True

Reason

The successor of a number is the number that comes directly after it. To find the successor, you add 1 to the number.

Successor of (−1) = −1 + 1 = 0.

Question 2(vii)

Write T for true and F for false statement :

|-15| + 10 = -5

Answer

False

Reason

The absolute value of −15 is 15.

⇒ ∣−15∣ + 10

⇒ 15 + 10

⇒ 25

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