There are 25% more grey stamps than purple stamps in a bag. After Tommy removed 40% of the grey stamps and increased the number of purple stamps by 20%, there are now 144 fewer grey stamps than purple stamps. Find the number of purple stamps at first.

	Grey	Purple
Before	5 u	4 u
Change	- 2 u	+ 0.8 u
After	3 u	4.8 u

Number of grey stamps in percentage
= 100% + 25%
= 125%

125% = ¹²⁵₁₀₀ = ⁵₄

Number of grey stamps that Tommy removed
= 40% x 5 u
= ⁴⁰₁₀₀ x 5 u 
= 2 u

Number of purple stamps that Tommy increased 
= 20% x 4 u
= ²⁰₁₀₀  x 4 u
= 0.8 u

Number of grey stamps in the end
= 5 u - 2 u
= 3 u

Number of purple stamps in the end
= 4 u + 0.8 u
= 4.8 u

Number of fewer grey stamps than purple stamps in the end
= 4.8 u - 3 u 
= 1.8 u 

1.8 u = 144

1 u = 144 ÷ 1.8 = 80

Number of purple stamps at first
= 4 u
= 4 x 80
= 320

Answer(s): 320