Betty made puffs for sale. 50% of the puffs were chocolate puffs and the rest were lotus paste and beef puffs in the ratio 3 : 1. If a customer bought 75% of the chocolate puffs and all of the beef puffs, what percentage of the lotus paste puffs must Betty 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	Lotus paste puffs	Beef puffs
1 u	1 u
	0.75 u	0.25 u

	Chocolate puffs	Lotus paste puffs	Beef puffs	Total puffs
Before	1 u	0.75 u	0.25 u	2 u
Change	- 0.75 u	- 0.5 u	- 0.25 u
After	0.25 u	0.25 u	0	0.5 u

50% = ⁵⁰₁₀₀ = ¹₂
75% = ⁷⁵₁₀₀ = ³₄

Total number of puffs = 2 u

Number of lotus paste and beef puffs
= 2 u - 1 u
= 1 u

Number of lotus paste puffs at first
= ³₄ x 1 u
= 0.75 u

Number of beef puffs at first
= 1 u - 0.75 u
= 0.25 u

Number of chocolate puffs sold
= 75% x 1 u
= ⁷⁵₁₀₀ x 1 u
= ³₄ x 1 u
= 0.75 u

Number of beef puffs sold
= ¹₄ x 1 u
= 0.25 u

Number of chocolate puffs left 
= 1 u - 0.75 u
= 0.25 u

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

Total number of puffs in the end to maintain the original percentage of chocolate puffs = 0.5 u

Number of lotus paste puffs left
= 0.5 u - 0.25 u
= 0.25 u

Number of lotus paste puffs that Betty must sell to maintain the original percentage of chocolate puffs
= 0.75 u - 0.25 u
= 0.5 u

Percentage of the lotus paste puffs that Betty must sell
= ^0.5_0.75 x 100%
= 66.7%

Answer(s): 66.7%