There are 25% more pink marbles than brown marbles in a bag. After John removed 20% of the pink marbles and increased the number of brown marbles by 20%, there are now 40 fewer pink marbles than brown marbles. Find the number of brown marbles at first.

	Pink	Brown
Before	5 u	4 u
Change	- 1 u	+ 0.8 u
After	4 u	4.8 u

Number of pink marbles in percentage
= 100% + 25%
= 125%

125% = ¹²⁵₁₀₀ = ⁵₄

Number of pink marbles that John removed
= 20% x 5 u
= ²⁰₁₀₀ x 5 u 
= 1 u

Number of brown marbles that John increased 
= 20% x 4 u
= ²⁰₁₀₀  x 4 u
= 0.8 u

Number of pink marbles in the end
= 5 u - 1 u
= 4 u

Number of brown marbles in the end
= 4 u + 0.8 u
= 4.8 u

Number of fewer pink marbles than brown marbles in the end
= 4.8 u - 4 u 
= 0.8 u 

0.8 u = 40

1 u = 40 ÷ 0.8 = 50

Number of brown marbles at first
= 4 u
= 4 x 50
= 200

Answer(s): 200