Winnie made buns for sale. 45% of the buns were chicken buns and the rest were beef and mushroom buns in the ratio 3 : 2. If a customer bought 80% of the chicken buns and all of the mushroom buns, what percentage of the beef buns must Winnie sell for her to maintain the original percentage of chicken buns at first? Leave your answer in decimals and correct to 1 decimal place.

Chicken buns	Beef buns	Mushroom buns
9 u	11 u
	6.6 u	4.4 u

	Chicken buns	Beef buns	Mushroom buns	Total buns
Before	9 u	6.6 u	4.4 u	20 u
Change	- 7.2 u	- 4.4 u	- 4.4 u
After	1.8 u	2.2 u	0	4 u

45% = ⁴⁵₁₀₀ = ⁹₂₀
80% = ⁸⁰₁₀₀ = ⁴₅

Total number of buns = 20 u

Number of beef and mushroom buns
= 20 u - 9 u
= 11 u

Number of beef buns at first
= ³₅ x 11 u
= 6.6 u

Number of mushroom buns at first
= 11 u - 6.6 u
= 4.4 u

Number of chicken buns sold
= 80% x 9 u
= ⁸⁰₁₀₀ x 9 u
= ⁴₅ x 9 u
= 7.2 u

Number of mushroom buns sold
= ²₅ x 11 u
= 4.4 u

Number of chicken buns left 
= 9 u - 7.2 u
= 1.8 u

To maintain the percentage of the chicken buns in the end, 
45% → 1.8 u
100% → ^1.8₄₅ x 100 = 4 u

Total number of buns in the end to maintain the original percentage of chicken buns = 4 u

Number of beef buns left
= 4 u - 1.8 u
= 2.2 u

Number of beef buns that Winnie must sell to maintain the original percentage of chicken buns
= 6.6 u - 2.2 u
= 4.4 u

Percentage of the beef buns that Winnie must sell
= ^4.4_6.6 x 100%
= 66.7%

Answer(s): 66.7%