There are 25% more white cards than red cards in a bag. After Peter removed 40% of the white cards and increased the number of red cards by 35%, there are now 120 fewer white cards than red cards. Find the number of red cards at first.

	White	Red
Before	5 u	4 u
Change	- 2 u	+ 1.4 u
After	3 u	5.4 u

Number of white cards in percentage
= 100% + 25%
= 125%

125% = ¹²⁵₁₀₀ = ⁵₄

Number of white cards that Peter removed
= 40% x 5 u
= ⁴⁰₁₀₀ x 5 u 
= 2 u

Number of red cards that Peter increased 
= 35% x 4 u
= ³⁵₁₀₀  x 4 u
= 1.4 u

Number of white cards in the end
= 5 u - 2 u
= 3 u

Number of red cards in the end
= 4 u + 1.4 u
= 5.4 u

Number of fewer white cards than red cards in the end
= 5.4 u - 3 u 
= 2.4 u 

2.4 u = 120

1 u = 120 ÷ 2.4 = 50

Number of red cards at first
= 4 u
= 4 x 50
= 200

Answer(s): 200