Nicole made sandwiches for sale. 40% of the sandwiches were mushroom sandwiches and the rest were chocolate and curry sandwiches in the ratio 3 : 2. If a customer bought 65% of the mushroom sandwiches and all of the curry sandwiches, what percentage of the chocolate sandwiches must Nicole sell for her to maintain the original percentage of mushroom sandwiches at first? Leave your answer in decimals and correct to 1 decimal place.

Mushroom sandwiches	Chocolate sandwiches	Curry sandwiches
2 u	3 u
	1.8 u	1.2 u

	Mushroom sandwiches	Chocolate sandwiches	Curry sandwiches	Total sandwiches
Before	2 u	1.8 u	1.2 u	5 u
Change	- 1.3 u	- 0.75 u	- 1.2 u
After	0.7 u	1.05 u	0	1.75 u

40% = ⁴⁰₁₀₀ = ²₅
65% = ⁶⁵₁₀₀ = ¹³₂₀

Total number of sandwiches = 5 u

Number of chocolate and curry sandwiches
= 5 u - 2 u
= 3 u

Number of chocolate sandwiches at first
= ³₅ x 3 u
= 1.8 u

Number of curry sandwiches at first
= 3 u - 1.8 u
= 1.2 u

Number of mushroom sandwiches sold
= 65% x 2 u
= ⁶⁵₁₀₀ x 2 u
= ¹³₂₀ x 2 u
= 1.3 u

Number of curry sandwiches sold
= ²₅ x 3 u
= 1.2 u

Number of mushroom sandwiches left 
= 2 u - 1.3 u
= 0.7 u

To maintain the percentage of the mushroom sandwiches in the end, 
40% → 0.7 u
100% → ^0.7₄₀ x 100 = 1.75 u

Total number of sandwiches in the end to maintain the original percentage of mushroom sandwiches = 1.75 u

Number of chocolate sandwiches left
= 1.75 u - 0.7 u
= 1.05 u

Number of chocolate sandwiches that Nicole must sell to maintain the original percentage of mushroom sandwiches
= 1.8 u - 1.05 u
= 0.75 u

Percentage of the chocolate sandwiches that Nicole must sell
= ^0.75_1.8 x 100%
= 41.7%

Answer(s): 41.7%