Olivia made muffins for sale. 45% of the muffins were mushroom muffins and the rest were sardine and lotus paste muffins in the ratio 4 : 1. If a customer bought 70% of the mushroom muffins and all of the lotus paste muffins, what percentage of the sardine muffins must Olivia 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	Sardine muffins	Lotus paste muffins
9 u	11 u
	8.8 u	2.2 u

	Mushroom muffins	Sardine muffins	Lotus paste muffins	Total muffins
Before	9 u	8.8 u	2.2 u	20 u
Change	- 6.3 u	- 5.5 u	- 2.2 u
After	2.7 u	3.3 u	0	6 u

45% = ⁴⁵₁₀₀ = ⁹₂₀
70% = ⁷⁰₁₀₀ = ⁷₁₀

Total number of muffins = 20 u

Number of sardine and lotus paste muffins
= 20 u - 9 u
= 11 u

Number of sardine muffins at first
= ⁴₅ x 11 u
= 8.8 u

Number of lotus paste muffins at first
= 11 u - 8.8 u
= 2.2 u

Number of mushroom muffins sold
= 70% x 9 u
= ⁷⁰₁₀₀ x 9 u
= ⁷₁₀ x 9 u
= 6.3 u

Number of lotus paste muffins sold
= ¹₅ x 11 u
= 2.2 u

Number of mushroom muffins left 
= 9 u - 6.3 u
= 2.7 u

To maintain the percentage of the mushroom muffins in the end, 
45% → 2.7 u
100% → ^2.7₄₅ x 100 = 6 u

Total number of muffins in the end to maintain the original percentage of mushroom muffins = 6 u

Number of sardine muffins left
= 6 u - 2.7 u
= 3.3 u

Number of sardine muffins that Olivia must sell to maintain the original percentage of mushroom muffins
= 8.8 u - 3.3 u
= 5.5 u

Percentage of the sardine muffins that Olivia must sell
= ^5.5_8.8 x 100%
= 62.5%

Answer(s): 62.5%