There were 223 white, yellow and grey notebooks in a box. 7 grey notebooks were removed from the box and the ratio of the number of white notebooks to the number of yellow notebooks to the number of grey notebooks became 2 : 3 : 7. Then some black notebooks were added and the ratio of the number of grey notebooks to the number of black notebooks was 7 : 2.

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

	White	Yellow	Grey	Black	Total
Before	2 u	3 u	7 u + 7	0	223
Change 1	No change	No change	- 7		- 7
After 1	2 u	3 u	7 u		216
Change 2	No change	No change	No change	+ 2 u
After 2	2 u	3 u	7 u	2 u

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

12 u + 7 = 223
12 u = 223 - 7
12 u = 216

1 u = 216 ÷ 12 = 18

Number of white notebooks at first
= 2 u
= 2 x 18
= 36

Number of yellow notebooks at first
= 3 u
= 3 x 18
= 54

Number of grey notebooks at first
= 7 u + 7
= 7 x 18 + 7
= 133 

At first
White notebooks : Yellow notebooks : Grey notebooks
36 : 54 : 133

(b)
Total number of notebooks in the box in the end
= 2 u + 3 u + 7 u + 2 u
= 14 u
= 252

Answer(s): (a) 36 : 54 : 133; (b) 252