Erika made buns for sale. 40% of the buns were sardine buns and the rest were curry and chicken buns in the ratio 3 : 1. If a customer bought 80% of the sardine buns and all of the chicken buns, what percentage of the curry buns must Erika sell for her to maintain the original percentage of sardine buns at first? Leave your answer in decimals and correct to 1 decimal place.

Sardine buns	Curry buns	Chicken buns
2 u	3 u
	2.25 u	0.75 u

	Sardine buns	Curry buns	Chicken buns	Total buns
Before	2 u	2.25 u	0.75 u	5 u
Change	- 1.6 u	- 1.65 u	- 0.75 u
After	0.4 u	0.6 u	0	1 u

40% = ⁴⁰₁₀₀ = ²₅
80% = ⁸⁰₁₀₀ = ⁴₅

Total number of buns = 5 u

Number of curry and chicken buns
= 5 u - 2 u
= 3 u

Number of curry buns at first
= ³₄ x 3 u
= 2.25 u

Number of chicken buns at first
= 3 u - 2.25 u
= 0.75 u

Number of sardine buns sold
= 80% x 2 u
= ⁸⁰₁₀₀ x 2 u
= ⁴₅ x 2 u
= 1.6 u

Number of chicken buns sold
= ¹₄ x 3 u
= 0.75 u

Number of sardine buns left 
= 2 u - 1.6 u
= 0.4 u

To maintain the percentage of the sardine buns in the end, 
40% → 0.4 u
100% → ^0.4₄₀ x 100 = 1 u

Total number of buns in the end to maintain the original percentage of sardine buns = 1 u

Number of curry buns left
= 1 u - 0.4 u
= 0.6 u

Number of curry buns that Erika must sell to maintain the original percentage of sardine buns
= 2.25 u - 0.6 u
= 1.65 u

Percentage of the curry buns that Erika must sell
= ^1.65_2.25 x 100%
= 73.3%

Answer(s): 73.3%