# Using Commutativity and Associativity of Addition of Rational Numbers, Express Each of the Following as a Rational Number: 3 7 + − 4 9 + − 11 7 + 7 9 - Mathematics

Sum

Using commutativity and associativity of addition of rational numbers, express each of the following as a rational number:

$\frac{3}{7} + \frac{- 4}{9} + \frac{- 11}{7} + \frac{7}{9}$

#### Solution

$\text{We have:}$
$\frac{3}{7} + \frac{- 4}{9} + \frac{- 11}{7} + \frac{7}{9}$
$= (\frac{3}{7} + \frac{- 11}{7}) + (\frac{- 4}{9} + \frac{7}{9})$
$= \left( \frac{3 - 11}{7} \right) + \left( \frac{- 4 + 7}{9} \right)$
$= \frac{- 8}{7} + \frac{3}{9}$
$= \frac{- 72 + 21}{63}$
$= \frac{- 51}{63}$
$= \frac{- 17}{21}$

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#### APPEARS IN

RD Sharma Class 8 Maths
Chapter 1 Rational Numbers
Exercise 1.2 | Q 5.2 | Page 14