A pile of 108 identical books has a mass of 30 kg. Find out the mass of 150 books and the number of books that has a mass of 20 kg.

A pile of 108 identical books has a mass of 30 kg.

Find out the

(a)the mass of 150 books and
(b)the number of books that has a mass of 20 kg.

Solution for (a) the mass of 150 books

Let be x = weight of 150 books.

So,

= 108 books : 30 kg

= 150 books : x kg

we can thus rewrite this as

`"108"/"30"` = `"150"/"x"`

= 3.6 = `"150"/"x"`

x = `"150"/"3.6"`

x = `"41.67"` kg

Solution for (b)the number of books that has a mass of 20 kg

let be y = number of books that has weight of 20 kg.

= 108 books : 30 kg

= y books : 20 kg

thus,

`"108"/"30"` = `"y"/"20"`

= 3.6 = `"y"/"20"`

y = 3.6 `\times` 20

y = 72 books