Question

If the weight of $81$ books is $9kg$, then:

The weight of $40$ such books is _____$kg$

Answer 1

Given that,

Weight of $81$ books $=$ $9kg$

By unitary method,

Divide both side by $81$

Weight of $1$ book $=$$\frac{9}{81}kg=\frac{1}{9}kg$

Multiply both side by $40$

Weight of $40$ books $=$$40\times \frac{1}{9}kg=4.4kg$

Hence, The weight of $40$ such books is $4.4kg$