Barbara made buns for sale. 40% of the buns were kaya buns and the rest were sardine and egg buns in the ratio 3 : 1. If a customer bought 60% of the kaya buns and all of the egg buns, what percentage of the sardine buns must Barbara sell for her to maintain the original percentage of kaya buns at first? Leave your answer in decimals and correct to 1 decimal place.

Kaya buns	Sardine buns	Egg buns
2 u	3 u
	2.25 u	0.75 u

	Kaya buns	Sardine buns	Egg buns	Total buns
Before	2 u	2.25 u	0.75 u	5 u
Change	- 1.2 u	- 1.05 u	- 0.75 u
After	0.8 u	1.2 u	0	2 u

40% = ⁴⁰₁₀₀ = ²₅
60% = ⁶⁰₁₀₀ = ³₅

Total number of buns = 5 u

Number of sardine and egg buns
= 5 u - 2 u
= 3 u

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

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

Number of kaya buns sold
= 60% x 2 u
= ⁶⁰₁₀₀ x 2 u
= ³₅ x 2 u
= 1.2 u

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

Number of kaya buns left 
= 2 u - 1.2 u
= 0.8 u

To maintain the percentage of the kaya buns in the end, 
40% → 0.8 u
100% → ^0.8₄₀ x 100 = 2 u

Total number of buns in the end to maintain the original percentage of kaya buns = 2 u

Number of sardine buns left
= 2 u - 0.8 u
= 1.2 u

Number of sardine buns that Barbara must sell to maintain the original percentage of kaya buns
= 2.25 u - 1.2 u
= 1.05 u

Percentage of the sardine buns that Barbara must sell
= ^1.05_2.25 x 100%
= 46.7%

Answer(s): 46.7%