Mary made croissants for sale. 50% of the croissants were egg croissants and the rest were curry and beef croissants in the ratio 4 : 1. If a customer bought 75% of the egg croissants and all of the beef croissants, what percentage of the curry croissants must Mary sell for her to maintain the original percentage of egg croissants at first? Leave your answer in decimals and correct to 1 decimal place.

Egg croissants	Curry croissants	Beef croissants
1 u	1 u
	0.8 u	0.2 u

	Egg croissants	Curry croissants	Beef croissants	Total croissants
Before	1 u	0.8 u	0.2 u	2 u
Change	- 0.75 u	- 0.55 u	- 0.2 u
After	0.25 u	0.25 u	0	0.5 u

50% = ⁵⁰₁₀₀ = ¹₂
75% = ⁷⁵₁₀₀ = ³₄

Total number of croissants = 2 u

Number of curry and beef croissants
= 2 u - 1 u
= 1 u

Number of curry croissants at first
= ⁴₅ x 1 u
= 0.8 u

Number of beef croissants at first
= 1 u - 0.8 u
= 0.2 u

Number of egg croissants sold
= 75% x 1 u
= ⁷⁵₁₀₀ x 1 u
= ³₄ x 1 u
= 0.75 u

Number of beef croissants sold
= ¹₅ x 1 u
= 0.2 u

Number of egg croissants left 
= 1 u - 0.75 u
= 0.25 u

To maintain the percentage of the egg croissants in the end, 
50% → 0.25 u
100% → ^0.25₅₀ x 100 = 0.5 u

Total number of croissants in the end to maintain the original percentage of egg croissants = 0.5 u

Number of curry croissants left
= 0.5 u - 0.25 u
= 0.25 u

Number of curry croissants that Mary must sell to maintain the original percentage of egg croissants
= 0.8 u - 0.25 u
= 0.55 u

Percentage of the curry croissants that Mary must sell
= ^0.55_0.8 x 100%
= 68.8%

Answer(s): 68.8%