Tim had 140 erasers. ³₄ were brown and the rest were grey and gold. The ratio of the number of grey erasers to the number of gold erasers was 1 : 4. Tim decided to give away some brown erasers to decrease the number of brown erasers to half of the total number of erasers.

1. How many more brown erasers than grey erasers did he have at first?
2. How many brown erasers did he have to give away?

Brown erasers	Grey erasers	Gold erasers	Total
3x5	1x5
	1x1	4x1
15 u	1 u	4 u	140

	Brown erasers	Grey erasers	Gold erasers
Before	15 u	1 u	4 u
Change	- ?
After	5 u	5 u
Comparing brown, grey and gold erasers in the end	1	1

(a)
The total number of grey erasers and gold erasers is repeated. Make the total number of grey erasers and gold erasers the same.  LCM of 1 and 5 is 5.

Total number of erasers at first
= 15 u + 1 u + 4 u
= 20 u

20 u = 140

1 u = 140 ÷ 20 = 7

Number of more brown erasers than grey erasers at first
= 15 u - 1 u
= 14 u
= 14 x 7
= 98

(b)
Number of more brown erasers that Tim had to give away
= 15 u - 5 u
= 10 u
= 10 x 7
= 70

Answer(s): (a) 98; (b) 70