Anna made puffs for sale. 40% of the puffs were chocolate puffs and the rest were mushroom and sardine puffs in the ratio 3 : 1. If a customer bought 75% of the chocolate puffs and all of the sardine puffs, what percentage of the mushroom puffs must Anna sell for her to maintain the original percentage of chocolate puffs at first? Leave your answer in decimals and correct to 1 decimal place.

Chocolate puffs	Mushroom puffs	Sardine puffs
2 u	3 u
	2.25 u	0.75 u

	Chocolate puffs	Mushroom puffs	Sardine puffs	Total puffs
Before	2 u	2.25 u	0.75 u	5 u
Change	- 1.5 u	- 1.5 u	- 0.75 u
After	0.5 u	0.75 u	0	1.25 u

40% = ⁴⁰₁₀₀ = ²₅
75% = ⁷⁵₁₀₀ = ³₄

Total number of puffs = 5 u

Number of mushroom and sardine puffs
= 5 u - 2 u
= 3 u

Number of mushroom puffs at first
= ³₄ x 3 u
= 2.25 u

Number of sardine puffs at first
= 3 u - 2.25 u
= 0.75 u

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

Number of sardine puffs sold
= ¹₄ x 3 u
= 0.75 u

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

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

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

Number of mushroom puffs left
= 1.25 u - 0.5 u
= 0.75 u

Number of mushroom puffs that Anna must sell to maintain the original percentage of chocolate puffs
= 2.25 u - 0.75 u
= 1.5 u

Percentage of the mushroom puffs that Anna must sell
= ^1.5_2.25 x 100%
= 66.7%

Answer(s): 66.7%