Question

Find the multiplicative inverse of $(-7{)}^{-2}÷(90{)}^{-1}$.
[3 marks]

Answer 1

We have ,$(-7{)}^{-2}÷(90{)}^{-1}=\frac{1}{(7{)}^2}÷\frac{1}{{90}^1}=\frac{1}{49}÷\frac{1}{90}=\frac{1}{49}\times \frac{90}{1}=\frac{90}{49}$

[2 marks]
'a' is called multiplactive inverse of 'b', if $a\times b=1$
Put b $=\frac{90}{49}\therefore a\times \frac{90}{49}=1\Rightarrow a=\frac{49}{90}$
[1 mark]