Math
posted by Julie Charmster .
A pile of 108 identical books has a mass of 30 kg.
Find
(a)the mass of 150 books and
(b)the number of books that has a mass of 20 kg

(a) to get this, we just use ratio and proportion:
let x = weight of 150 books.
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
(b) we also use ratio and proportion here:
let 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*20
y = 72 books
hope this helps~ :) 
(a)
the mass of 108 books=30 kg
the mass of one book=30/108
the mass of 150 books=150*5/8
=125/8 kg 
Ans.
30/108=5/18
5/15 x 150=41. 2/3kg
Please correct me! 
(a)150/108=a/30
108*a=150*30
150*30/108
75*15/27
1125/27
41.66
(b)108/a=30/20
3a=10821*2
108*2/3a
216/3=72