Emily bought a total of 150 big and small chocolate bars. Then she decided to exchange 75% of her big chocolate bars for the small ones in the ratio of 3 : 8. After the exchange, she had 165 chocolate bars. What percentage of the chocolate bars she bought were small ones?

	Big chocolate bars	Small chocolate bars	Total
Before	4 u	?	150
Change	- 3 u
Comparing big and small chocolate bars at exchange	- 3 u	+ 8 u	+ 15
After	1 u	?	165

75% = ⁷⁵₁₀₀ = ³₄

The number of big chocolate bars that were exchanged for small chocolate bars was repeated.  

Number of extra chocolate bars that Emily received due to the exchange
= 8 u - 3 u
= 5 u

5 u = 165 - 150
5 u = 15

1 u = 15 ÷ 5 = 3

Number of small chocolate bars at first
= 150 - 4 u
= 150 - 4 x 3
= 150 - 12
= 138

Percentage of the chocolate bars Emily bought that were small ones
=  ¹³⁸₁₅₀ x 100%
= 92% 

Answer(s): 92%