Nicole made buns for sale. 60% of the buns were chocolate buns and the rest were beef and sardine buns in the ratio 4 : 1. If a customer bought 65% of the chocolate buns and all of the sardine buns, what percentage of the beef buns must Nicole sell for her to maintain the original percentage of chocolate buns at first? Leave your answer in decimals and correct to 1 decimal place.

Chocolate buns	Beef buns	Sardine buns
3 u	2 u
	1.6 u	0.4 u

	Chocolate buns	Beef buns	Sardine buns	Total buns
Before	3 u	1.6 u	0.4 u	5 u
Change	- 1.95 u	- 0.9 u	- 0.4 u
After	1.05 u	0.7 u	0	1.75 u

60% = ⁶⁰₁₀₀ = ³₅
65% = ⁶⁵₁₀₀ = ¹³₂₀

Total number of buns = 5 u

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

Number of beef buns at first
= ⁴₅ x 2 u
= 1.6 u

Number of sardine buns at first
= 2 u - 1.6 u
= 0.4 u

Number of chocolate buns sold
= 65% x 3 u
= ⁶⁵₁₀₀ x 3 u
= ¹³₂₀ x 3 u
= 1.95 u

Number of sardine buns sold
= ¹₅ x 2 u
= 0.4 u

Number of chocolate buns left 
= 3 u - 1.95 u
= 1.05 u

To maintain the percentage of the chocolate buns in the end, 
60% → 1.05 u
100% → ^1.05₆₀ x 100 = 1.75 u

Total number of buns in the end to maintain the original percentage of chocolate buns = 1.75 u

Number of beef buns left
= 1.75 u - 1.05 u
= 0.7 u

Number of beef buns that Nicole must sell to maintain the original percentage of chocolate buns
= 1.6 u - 0.7 u
= 0.9 u

Percentage of the beef buns that Nicole must sell
= ^0.9_1.6 x 100%
= 56.3%

Answer(s): 56.3%