There were 92 green, yellow and blue notebooks in a box. 12 blue notebooks were removed from the box and the ratio of the number of green notebooks to the number of yellow notebooks to the number of blue notebooks became 2 : 5 : 9. Then some purple notebooks were added and the ratio of the number of blue notebooks to the number of purple notebooks was 9 : 5.

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

	Green	Yellow	Blue	Purple	Total
Before	2 u	5 u	9 u + 12	0	92
Change 1	No change	No change	- 12		- 12
After 1	2 u	5 u	9 u		80
Change 2	No change	No change	No change	+ 5 u
After 2	2 u	5 u	9 u	5 u

(a)
Total number of notebooks at first
= 2 u + 5 u + 9 u + 12
= 16 u + 12

16 u + 12 = 92
16 u = 92 - 12
16 u = 80

1 u = 80 ÷ 16 = 5

Number of green notebooks at first
= 2 u
= 2 x 5
= 10

Number of yellow notebooks at first
= 5 u
= 5 x 5
= 25

Number of blue notebooks at first
= 9 u + 12
= 9 x 5 + 12
= 57 

At first
Green notebooks : Yellow notebooks : Blue notebooks
10 : 25 : 57

(b)
Total number of notebooks in the box in the end
= 2 u + 5 u + 9 u + 5 u
= 21 u
= 105

Answer(s): (a) 10 : 25 : 57; (b) 105