There are 25% more green coins than white coins in a bag. After Ben removed 20% of the green coins and increased the number of white coins by 30%, there are now 120 fewer green coins than white coins. Find the number of white coins at first.

	Green	White
Before	5 u	4 u
Change	- 1 u	+ 1.2 u
After	4 u	5.2 u

Number of green coins in percentage
= 100% + 25%
= 125%

125% = ¹²⁵₁₀₀ = ⁵₄

Number of green coins that Ben removed
= 20% x 5 u
= ²⁰₁₀₀ x 5 u 
= 1 u

Number of white coins that Ben increased 
= 30% x 4 u
= ³⁰₁₀₀  x 4 u
= 1.2 u

Number of green coins in the end
= 5 u - 1 u
= 4 u

Number of white coins in the end
= 4 u + 1.2 u
= 5.2 u

Number of fewer green coins than white coins in the end
= 5.2 u - 4 u 
= 1.2 u 

1.2 u = 120

1 u = 120 ÷ 1.2 = 100

Number of white coins at first
= 4 u
= 4 x 100
= 400

Answer(s): 400