Adam has 40 blue stickers and 210 green stickers.
After buying the same number of stickers,
the ratio of the blue stickers and the green stickers becomes 3 : 8.
How many stickers does he buy?

	Blue	Green	Difference
Before	40	210	170
Change	+ ?	+ ?
After	3 u	8 u	5 u

At first
Difference in the number of stickers
= 210 - 40
= 170

In the end
Number of blue stickers = 3 u
Number of green stickers = 8 u

Difference in the number of stickers in units
= 8 u - 3 u
= 5 u

The difference in the number of stickers between the blue stickers and the green stickers remains unchanged.

5 u = 170

1 u = 170 ÷ 5 = 34

Number of blue stickers that Adam buys
= 3 u - 40
= 3 x 34 - 40
= 102 - 40
= 62

Total number of stickers that Adam buys
= 2 x 62
= 124

Answer(s): 124