Joelle made buns for sale. 50% of the buns were curry buns and the rest were chicken and sardine buns in the ratio 4 : 1. If a customer bought 85% of the curry buns and all of the sardine buns, what percentage of the chicken buns must Joelle sell for her to maintain the original percentage of curry buns at first? Leave your answer in decimals and correct to 1 decimal place.

Curry buns	Chicken buns	Sardine buns
1 u	1 u
	0.8 u	0.2 u

	Curry buns	Chicken buns	Sardine buns	Total buns
Before	1 u	0.8 u	0.2 u	2 u
Change	- 0.85 u	- 0.65 u	- 0.2 u
After	0.15 u	0.15 u	0	0.3 u

50% = ⁵⁰₁₀₀ = ¹₂
85% = ⁸⁵₁₀₀ = ¹⁷₂₀

Total number of buns = 2 u

Number of chicken and sardine buns
= 2 u - 1 u
= 1 u

Number of chicken buns at first
= ⁴₅ x 1 u
= 0.8 u

Number of sardine buns at first
= 1 u - 0.8 u
= 0.2 u

Number of curry buns sold
= 85% x 1 u
= ⁸⁵₁₀₀ x 1 u
= ¹⁷₂₀ x 1 u
= 0.85 u

Number of sardine buns sold
= ¹₅ x 1 u
= 0.2 u

Number of curry buns left 
= 1 u - 0.85 u
= 0.15 u

To maintain the percentage of the curry buns in the end, 
50% → 0.15 u
100% → ^0.15₅₀ x 100 = 0.3 u

Total number of buns in the end to maintain the original percentage of curry buns = 0.3 u

Number of chicken buns left
= 0.3 u - 0.15 u
= 0.15 u

Number of chicken buns that Joelle must sell to maintain the original percentage of curry buns
= 0.8 u - 0.15 u
= 0.65 u

Percentage of the chicken buns that Joelle must sell
= ^0.65_0.8 x 100%
= 81.3%

Answer(s): 81.3%