Gabby had 175 stickers. ²₅ were grey and the rest were silver and yellow. The ratio of the number of silver stickers to the number of yellow stickers was 1 : 4. Gabby decided to buy some more grey stickers to increase the number of grey stickers to half of the total number of stickers.

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

Grey stickers	Silver stickers	Yellow stickers	Total
2x5	3x5
	1x3	4x3
10 u	3 u	12 u	175

	Grey stickers	Silver stickers	Yellow stickers
Before	10 u	3 u	12 u
Change	+ ?
After	15 u	15 u
Comparing grey, silver and yellow stickers in the end	1	1

(a)
The total number of silver stickers and yellow stickers is repeated. Make the total number of silver stickers and yellow stickers the same.  LCM of 3 and 5 is 15.

Total number of stickers at first
= 10 u + 3 u + 12 u
= 25 u

25 u = 175

1 u = 175 ÷ 25 = 7

Number of less silver stickers than grey stickers at first
= 10 u - 3 u
= 7 u
= 7 x 7
= 49

(b)
Number of more grey stickers that Gabby had to buy
= 15 u - 10 u
= 5 u
= 5 x 7
= 35

Answer(s): (a) 49; (b) 35