Adam has 30 green stickers and 250 blue stickers.
After buying the same number of stickers,
the ratio of the green stickers and the blue stickers becomes 2 : 7.
How many stickers does he buy?

	Green	Blue	Difference
Before	30	250	220
Change	+ ?	+ ?
After	2 u	7 u	5 u

At first
Difference in the number of stickers
= 250 - 30
= 220

In the end
Number of green stickers = 2 u
Number of blue stickers = 7 u

Difference in the number of stickers in units
= 7 u - 2 u
= 5 u

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

5 u = 220

1 u = 220 ÷ 5 = 44

Number of green stickers that Adam buys
= 2 u - 30
= 2 x 44 - 30
= 88 - 30
= 58

Total number of stickers that Adam buys
= 2 x 58
= 116

Answer(s): 116