Nora made buns for sale. 45% of the buns were chocolate buns and the rest were curry and beef buns in the ratio 3 : 1. If a customer bought 80% of the chocolate buns and all of the beef buns, what percentage of the curry buns must Nora 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	Curry buns	Beef buns
9 u	11 u
	8.25 u	2.75 u

	Chocolate buns	Curry buns	Beef buns	Total buns
Before	9 u	8.25 u	2.75 u	20 u
Change	- 7.2 u	- 6.05 u	- 2.75 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 curry and beef buns
= 20 u - 9 u
= 11 u

Number of curry buns at first
= ³₄ x 11 u
= 8.25 u

Number of beef buns at first
= 11 u - 8.25 u
= 2.75 u

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

Number of beef buns sold
= ¹₄ x 11 u
= 2.75 u

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

To maintain the percentage of the chocolate 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 chocolate buns = 4 u

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

Number of curry buns that Nora must sell to maintain the original percentage of chocolate buns
= 8.25 u - 2.2 u
= 6.05 u

Percentage of the curry buns that Nora must sell
= ^6.05_8.25 x 100%
= 73.3%

Answer(s): 73.3%