There are 25% more purple stamps than black stamps in a bag. After John removed 40% of the purple stamps and increased the number of black stamps by 30%, there are now 176 fewer purple stamps than black stamps. Find the number of black stamps at first.

	Purple	Black
Before	5 u	4 u
Change	- 2 u	+ 1.2 u
After	3 u	5.2 u

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

125% = ¹²⁵₁₀₀ = ⁵₄

Number of purple stamps that John removed
= 40% x 5 u
= ⁴⁰₁₀₀ x 5 u 
= 2 u

Number of black stamps that John increased 
= 30% x 4 u
= ³⁰₁₀₀  x 4 u
= 1.2 u

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

Number of black stamps in the end
= 4 u + 1.2 u
= 5.2 u

Number of fewer purple stamps than black stamps in the end
= 5.2 u - 3 u 
= 2.2 u 

2.2 u = 176

1 u = 176 ÷ 2.2 = 80

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

Answer(s): 320