Nora had 420 stickers. ²₇ were green and the rest were silver and red. The ratio of the number of silver stickers to the number of red stickers was 1 : 5. Nora decided to buy some more green stickers to increase the number of green stickers to half of the total number of stickers.

1. How many less silver stickers than green stickers did he have at first?
2. How many more green stickers did he have to buy?

Green stickers	Silver stickers	Red stickers	Total
2x6	5x6
	1x5	5x5
12 u	5 u	25 u	420

	Green stickers	Silver stickers	Red stickers
Before	12 u	5 u	25 u
Change	+ ?
After	30 u	30 u
Comparing green, silver and red stickers in the end	1	1

(a)
The total number of silver stickers and red stickers is repeated. Make the total number of silver stickers and red stickers the same.  LCM of 5 and 6 is 30.

Total number of stickers at first
= 12 u + 5 u + 25 u
= 42 u

42 u = 420

1 u = 420 ÷ 42 = 10

Number of less silver stickers than green stickers at first
= 12 u - 5 u
= 7 u
= 7 x 10
= 70

(b)
Number of more green stickers that Nora had to buy
= 30 u - 12 u
= 18 u
= 18 x 10
= 180

Answer(s): (a) 70; (b) 180