Find the multiplicative inverse (reciprocal) of each of the following rational numbers:
(i) 9
(ii) $ -7 $
(iii) $ \frac{12}{5} $
(iv) $ \frac{-7}{9} $
(v) $ \frac{-3}{-5} $
(vi) $ \frac{2}{3} \times \frac{9}{4} $
(vii) $ \frac{-5}{8} \times \frac{16}{15} $
(viii) $ -2 \times \frac{-3}{5} $
(ix)-1 $
(x) \frac{0}{3} $
(xi) 1


To do:

We have to find the multiplicative inverse of the given rational numbers.

Solution:

The multiplicative inverse is that number which makes the existing number equal to unity on multiplication.

Multiplicative inverse of $a$ is $\frac{1}{a}$.

Therefore,

(i) The multiplicative inverse of $9=\frac{1}{9}$ 

$=\frac{1}{9}$

The multiplicative inverse of $9$ is $\frac{1}{9}$.

(ii) The multiplicative inverse of $-7=\frac{1}{-7}$ 

$=\frac{-1}{7}$ 

The multiplicative inverse of $-7$ is $\frac{-1}{7}$.

(iii)The multiplicative inverse of $\frac{12}{5}=\frac{1}{\frac{12}{5}}$ 

$=\frac{5}{12}$ 

The multiplicative inverse of $\frac{12}{5}$ is $\frac{5}{12}$.  

(iv) The multiplicative inverse of $\frac{-7}{9}=\frac{1}{\frac{-7}{9}}$ 

$=\frac{-9}{7}$ 

The multiplicative inverse of $\frac{-7}{9}$ is $\frac{-9}{7}$.   

(v) The multiplicative inverse of $\frac{-3}{-5}=\frac{1}{\frac{-3}{-5}}$ 

$=\frac{-5}{-3}$

$=\frac{5}{3}$ 

The multiplicative inverse of $\frac{-3}{-5}$ is $\frac{5}{3}$.    

(vi) $\frac{2}{3} \times \frac{9}{4}=\frac{2\times9}{3\times4}$

$=\frac{3}{2}$

Therefore,

The multiplicative inverse of $\frac{3}{2}=\frac{1}{\frac{3}{2}}$ 

$=\frac{2}{3}$ 

The multiplicative inverse of $\frac{2}{3}\times\frac{9}{4}$ is $\frac{2}{3}$.    

(vii) $\frac{-5}{8} \times \frac{16}{15}=\frac{-5\times16}{8\times15}$

$=\frac{-2}{3}$

Therefore,

The multiplicative inverse of $\frac{-2}{3}=\frac{1}{\frac{-2}{3}}$ 

$=\frac{-3}{2}$ 

The multiplicative inverse of $\frac{-5}{8}\times\frac{16}{15}$ is $\frac{-3}{2}$.

(viii) $-2 \times \frac{-3}{5}=\frac{-2\times(-3)}{5}$

$=\frac{6}{5}$

Therefore,

The multiplicative inverse of $\frac{6}{5}=\frac{1}{\frac{6}{5}}$ 

$=\frac{5}{6}$ 

The multiplicative inverse of $-2\times\frac{-3}{5}$ is $\frac{5}{6}$.      

(ix) The multiplicative inverse of $-1=\frac{1}{-1}$ 

$=-1$ 

The multiplicative inverse of $-1$ is $-1$.       

(x)$\frac{0}{3}=0$

$=0$

Therefore,

The multiplicative inverse of $0$ is not defined as any number divided by 0 is not defined.

(xi)The multiplicative inverse of $1=\frac{1}{1}$ 

$=1$ 

The multiplicative inverse of $1$ is $1$.       

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Updated on: 10-Oct-2022

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