Fabian had 70 pens. ⁴₇ were silver and the rest were grey and blue. The ratio of the number of grey pens to the number of blue pens was 1 : 4. Fabian decided to give away some silver pens to decrease the number of silver pens to half of the total number of pens.

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

Silver pens	Grey pens	Blue pens	Total
4x5	3x5
	1x3	4x3
20 u	3 u	12 u	70

	Silver pens	Grey pens	Blue pens
Before	20 u	3 u	12 u
Change	- ?
After	15 u	15 u
Comparing silver, grey and blue pens in the end	1	1

(a)
The total number of grey pens and blue pens is repeated. Make the total number of grey pens and blue pens the same.  LCM of 3 and 5 is 15.

Total number of pens at first
= 20 u + 3 u + 12 u
= 35 u

35 u = 70

1 u = 70 ÷ 35 = 2

Number of more silver pens than grey pens at first
= 20 u - 3 u
= 17 u
= 17 x 2
= 34

(b)
Number of more silver pens that Fabian had to give away
= 20 u - 15 u
= 5 u
= 5 x 2
= 10

Answer(s): (a) 34; (b) 10