Yoko bought a total of 400 big and small chocolate bars. Then she decided to exchange 25% of her big chocolate bars for the small ones in the ratio of 1 : 4. After the exchange, she had 424 chocolate bars. What percentage of the chocolate bars she bought were small ones?

	Big chocolate bars	Small chocolate bars	Total
Before	4 u	?	400
Change	- 1 u
Comparing big and small chocolate bars at exchange	- 1 u	+ 4 u	+ 24
After	3 u	?	424

25% = ²⁵₁₀₀ = ¹₄

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

Number of extra chocolate bars that Yoko received due to the exchange
= 4 u - 1 u
= 3 u

3 u = 424 - 400
3 u = 24

1 u = 24 ÷ 3 = 8

Number of small chocolate bars at first
= 400 - 4 u
= 400 - 4 x 8
= 400 - 32
= 368

Percentage of the chocolate bars Yoko bought that were small ones
=  ³⁶⁸₄₀₀ x 100%
= 92% 

Answer(s): 92%