Anna made muffins for sale. 40% of the muffins were chocolate muffins and the rest were sardine and beef muffins in the ratio 2 : 1. If a customer bought 75% of the chocolate muffins and all of the beef muffins, what percentage of the sardine muffins must Anna sell for her to maintain the original percentage of chocolate muffins at first? Leave your answer in decimals and correct to 1 decimal place.

Chocolate muffins	Sardine muffins	Beef muffins
2 u	3 u
	2 u	1 u

	Chocolate muffins	Sardine muffins	Beef muffins	Total muffins
Before	2 u	2 u	1 u	5 u
Change	- 1.5 u	- 1.25 u	- 1 u
After	0.5 u	0.75 u	0	1.25 u

40% = ⁴⁰₁₀₀ = ²₅
75% = ⁷⁵₁₀₀ = ³₄

Total number of muffins = 5 u

Number of sardine and beef muffins
= 5 u - 2 u
= 3 u

Number of sardine muffins at first
= ²₃ x 3 u
= 2 u

Number of beef muffins at first
= 3 u - 2 u
= 1 u

Number of chocolate muffins sold
= 75% x 2 u
= ⁷⁵₁₀₀ x 2 u
= ³₄ x 2 u
= 1.5 u

Number of beef muffins sold
= ¹₃ x 3 u
= 1 u

Number of chocolate muffins left 
= 2 u - 1.5 u
= 0.5 u

To maintain the percentage of the chocolate muffins in the end, 
40% → 0.5 u
100% → ^0.5₄₀ x 100 = 1.25 u

Total number of muffins in the end to maintain the original percentage of chocolate muffins = 1.25 u

Number of sardine muffins left
= 1.25 u - 0.5 u
= 0.75 u

Number of sardine muffins that Anna must sell to maintain the original percentage of chocolate muffins
= 2 u - 0.75 u
= 1.25 u

Percentage of the sardine muffins that Anna must sell
= ^1.25₂ x 100%
= 62.5%

Answer(s): 62.5%