There were 79 silver, purple and pink notebooks in a box. 9 pink notebooks were removed from the box and the ratio of the number of silver notebooks to the number of purple notebooks to the number of pink notebooks became 5 : 2 : 7. Then some blue notebooks were added and the ratio of the number of pink notebooks to the number of blue notebooks was 7 : 4.

1. What was the ratio of the number of silver notebooks to the number of purple notebooks to the number of pink notebooks at first?
2. How many notebooks were in the box in the end?

	Silver	Purple	Pink	Blue	Total
Before	5 u	2 u	7 u + 9	0	79
Change 1	No change	No change	- 9		- 9
After 1	5 u	2 u	7 u		70
Change 2	No change	No change	No change	+ 4 u
After 2	5 u	2 u	7 u	4 u

(a)
Total number of notebooks at first
= 5 u + 2 u + 7 u + 9
= 14 u + 9

14 u + 9 = 79
14 u = 79 - 9
14 u = 70

1 u = 70 ÷ 14 = 5

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

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

Number of pink notebooks at first
= 7 u + 9
= 7 x 5 + 9
= 44 

At first
Silver notebooks : Purple notebooks : Pink notebooks
25 : 10 : 44

(b)
Total number of notebooks in the box in the end
= 5 u + 2 u + 7 u + 4 u
= 18 u
= 90

Answer(s): (a) 25 : 10 : 44; (b) 90