Emily made muffins for sale. 55% of the muffins were mushroom muffins and the rest were chocolate and sardine muffins in the ratio 3 : 2. If a customer bought 80% of the mushroom muffins and all of the sardine muffins, what percentage of the chocolate muffins must Emily sell for her to maintain the original percentage of mushroom muffins at first? Leave your answer in decimals and correct to 1 decimal place.

Mushroom muffins	Chocolate muffins	Sardine muffins
11 u	9 u
	5.4 u	3.6 u

	Mushroom muffins	Chocolate muffins	Sardine muffins	Total muffins
Before	11 u	5.4 u	3.6 u	20 u
Change	- 8.8 u	- 3.6 u	- 3.6 u
After	2.2 u	1.8 u	0	4 u

55% = ⁵⁵₁₀₀ = ¹¹₂₀
80% = ⁸⁰₁₀₀ = ⁴₅

Total number of muffins = 20 u

Number of chocolate and sardine muffins
= 20 u - 11 u
= 9 u

Number of chocolate muffins at first
= ³₅ x 9 u
= 5.4 u

Number of sardine muffins at first
= 9 u - 5.4 u
= 3.6 u

Number of mushroom muffins sold
= 80% x 11 u
= ⁸⁰₁₀₀ x 11 u
= ⁴₅ x 11 u
= 8.8 u

Number of sardine muffins sold
= ²₅ x 9 u
= 3.6 u

Number of mushroom muffins left 
= 11 u - 8.8 u
= 2.2 u

To maintain the percentage of the mushroom muffins in the end, 
55% → 2.2 u
100% → ^2.2₅₅ x 100 = 4 u

Total number of muffins in the end to maintain the original percentage of mushroom muffins = 4 u

Number of chocolate muffins left
= 4 u - 2.2 u
= 1.8 u

Number of chocolate muffins that Emily must sell to maintain the original percentage of mushroom muffins
= 5.4 u - 1.8 u
= 3.6 u

Percentage of the chocolate muffins that Emily must sell
= ^3.6_5.4 x 100%
= 66.7%

Answer(s): 66.7%