Adam has 60 green stickers and 240 red stickers.
After buying the same number of stickers,
the ratio of the green stickers and the red stickers becomes 3 : 5.
How many stickers does he buy?

	Green	Red	Difference
Before	60	240	180
Change	+ ?	+ ?
After	3 u	5 u	2 u

At first
Difference in the number of stickers
= 240 - 60
= 180

In the end
Number of green stickers = 3 u
Number of red 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 green stickers and the red stickers remains unchanged.

2 u = 180

1 u = 180 ÷ 2 = 90

Number of green stickers that Adam buys
= 3 u - 60
= 3 x 90 - 60
= 270 - 60
= 210

Total number of stickers that Adam buys
= 2 x 210
= 420

Answer(s): 420