Answer:
The mass of 150 books = 41.7kg
The number of books that have mass 20kg = 72 books
Step-by-step explanation:
(I) Number of identical books = 108
Mass of books = 30 kg
Mass of 150 books = ?
Let the mass of 150 books = x kg
To find the mass of 150 books we will use ratio and proportion:
108 books: 30kg = 150 books: x kg
You can also write it like this because ratio can be written in division:
108/30 = 150/x
By cross multiplication:
108x = 150*30
108 x= 4500
Divide both sides by 108
108 x/108 = 4500/108
x= 41.7
Thus the mass of 150 books = 41.7kg
( ii ) The number of books that have a mass of 20 kg = ?
Let assume that the number of books of mass 20 kg = y books
We will again use ratio and proportion method.
108 books: 30kg = y: 20kg
We can write it as:
108/30 = y/20
By cross multiplication:
108 *20 = 30y
2160= 30y
Divide both the terms by 30
2160/30 = 30y/30
72 = y
Therefore the number of books that have mass 20kg = 72 books ....
