Question

Class 8

Cw:4

Chapter :1

Rational Numbers

DATE: 24/03/2021

Rational Numbers



Associative property



Properties of the types of numbers – Associative



A set of numbers is said to be associative for a specific mathematical operation if the result obtained when changing grouping (parenthesizing) of the operands does not change the result.

Whole Numbers

Addition – Changing the grouping of operands in addition of whole numbers does not change the result. Hence, whole numbers under addition are associative.

2 + (3 + 6) = (2 + 3) + 6

(0 + 6)+ 8 = 0 + (6 + 8)

Subtraction - Changing the grouping of operands in subtraction of whole numbers changes the result. Hence, whole numbers under subtraction are not associative.

5 - (3 - 4) ≠ (5 - 3) - 4

(2 - 0) - 6 ≠ 2 - (0 - 6)

Multiplication - Changing the grouping of operands in multiplication of whole numbers does not change the result. Hence, whole numbers under multiplication are associative.

5 x (3 x 6) = (5 x 3) x 6

(2 x 0)x 9 = 2



Class 8

Chapter :1 “Rational Numbers”

4. By what rational number should 22/7 be divided, to get the number - 11/24?

5. Represent the following rational numbers on the number line. (i) -3/10 (ii) 8/7 (iii) -5/9 (iv)21/7

6. Find two rational numbers between (i) -3 and 3. (ii) 0 and 1.

7. Insert six rational numbers between (i) -1/4 and -2/5 (ii) 21/12 and 12/21.

8. Find five rational no.s between 1/8 and 2/8

9. Multiply the negative of 2/3 by the inverse of 9/7.

10. What should be added to -16/3 to make it 1/9?

11. What should be subtracted from 5/8 to make it -1?

12. Multiply the negative of 29/2 by its reciprocal.



14. Write a rational number equivalent to 18/29 having 87 as denominator.

15. Write 2/3, -4/9, -8/11 in ascending order.

16. Write 2/3, -4/9, -8/11 in descending order.

17. Verify that –(-x) = x for:-

(a) 7/9 (b) -5/11

18. Using properties find the value of:-

(i) (3/7 × 5/6) + (3/7 × 12/13)



(ii) (-8/3 × 5/6) + (-13/12 × 5/6)

19. Name the property of multiplication illustrated by the following statements:



(i) -11/13 × -17/5 = -17/5 × -11/13



(ii) {(-2)/3 × 7/9} × (-9)/5 = (-2)/3 × {7/9 × (-9)/5}



(iii) (-3)/4 × {(-5)/6 + 7/8 = {(-3)/4 × (-5)/6} + {(-3)/4 × 7/8}



(iv) (-16)/9 × 1 = 1 × (-16)/9 = (-16)/9



(v) (-11)/15 × 15/-11 = 15/-11 × (-11)/15 = 1



(vi) -7/5 × 0 = 0

20. Find the sum of additive inverse and multiplicative inverse of 7. ​

Answer 1

we don't teach it cmpletly