Adam has 70 blue stickers and 290 green stickers.
After buying the same number of stickers,
the ratio of the blue stickers and the green stickers becomes 3 : 5.
How many stickers does he buy?

	Blue	Green	Difference
Before	70	290	220
Change	+ ?	+ ?
After	3 u	5 u	2 u

At first
Difference in the number of stickers
= 290 - 70
= 220

In the end
Number of blue stickers = 3 u
Number of green stickers = 5 u

Difference in the number of stickers in units
= 5 u - 3 u
= 2 u

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

2 u = 220

1 u = 220 ÷ 2 = 110

Number of blue stickers that Adam buys
= 3 u - 70
= 3 x 110 - 70
= 330 - 70
= 260

Total number of stickers that Adam buys
= 2 x 260
= 520

Answer(s): 520