Question

The weight of $72$ books is $9\text{kg}$. What is the weight of $40$ such books $?$

Answer 1

Finding weight of books:

Weight of $72$ books $=9\text{kg}$

Weight of $1$ book $=\frac{9}{72}\text{kg}$

Weight of $40$ books $=\frac{9}{72}\times 40=\frac{\sout{9}}{\sout{72}}\times 40=\frac{1}{\sout{8}}\times \sout{40}=5\text{kg}$

Hence, weight of $40$books is $5\text{kg}$.