There were 129 silver, green and blue staplers in a box. 9 blue staplers were removed from the box and the ratio of the number of silver staplers to the number of green staplers to the number of blue staplers became 2 : 3 : 7. Then some red staplers were added and the ratio of the number of blue staplers to the number of red staplers was 7 : 4.

1. What was the ratio of the number of silver staplers to the number of green staplers to the number of blue staplers at first?
2. How many staplers were in the box in the end?

	Silver	Green	Blue	Red	Total
Before	2 u	3 u	7 u + 9	0	129
Change 1	No change	No change	- 9		- 9
After 1	2 u	3 u	7 u		120
Change 2	No change	No change	No change	+ 4 u
After 2	2 u	3 u	7 u	4 u

(a)
Total number of staplers at first
= 2 u + 3 u + 7 u + 9
= 12 u + 9

12 u + 9 = 129
12 u = 129 - 9
12 u = 120

1 u = 120 ÷ 12 = 10

Number of silver staplers at first
= 2 u
= 2 x 10
= 20

Number of green staplers at first
= 3 u
= 3 x 10
= 30

Number of blue staplers at first
= 7 u + 9
= 7 x 10 + 9
= 79 

At first
Silver staplers : Green staplers : Blue staplers
20 : 30 : 79

(b)
Total number of staplers in the box in the end
= 2 u + 3 u + 7 u + 4 u
= 16 u
= 160

Answer(s): (a) 20 : 30 : 79; (b) 160