Question

The weight of 72 books is 9 kg.

(a)what is the weight of 85 such books?

(b)how many such books weigh 18 kg?

Answer 1

weight of 72 books = 9 kg
weight of 1 book = $\frac{9}{72}kg$
weight of 85 books = $\frac{9}{72}\times 85=\frac{85}{8}=10.625kg$
no. of books whose weight is 9 kg = 72
no. of books whose weight is 1 kg = $\frac{72}{9}=8$
no. of books whose weight is 18 kg = 8 $\times$ 18 = 144