Jean had 70 coins. ³₇ were pink and the rest were brown and grey. The ratio of the number of brown coins to the number of grey coins was 1 : 4. Jean decided to buy some more pink coins to increase the number of pink coins to half of the total number of coins.

1. How many less brown coins than pink coins did he have at first?
2. How many more pink coins did he have to buy?

Pink coins	Brown coins	Grey coins	Total
3x5	4x5
	1x4	4x4
15 u	4 u	16 u	70

	Pink coins	Brown coins	Grey coins
Before	15 u	4 u	16 u
Change	+ ?
After	20 u	20 u
Comparing pink, brown and grey coins in the end	1	1

(a)
The total number of brown coins and grey coins is repeated. Make the total number of brown coins and grey coins the same.  LCM of 4 and 5 is 20.

Total number of coins at first
= 15 u + 4 u + 16 u
= 35 u

35 u = 70

1 u = 70 ÷ 35 = 2

Number of less brown coins than pink coins at first
= 15 u - 4 u
= 11 u
= 11 x 2
= 22

(b)
Number of more pink coins that Jean had to buy
= 20 u - 15 u
= 5 u
= 5 x 2
= 10

Answer(s): (a) 22; (b) 10