Billy had to paint some containers. On the first day, the number of containers he painted was 30% of the number of containers that he had not painted. One week later, he painted another 389 containers. As a result, the total number of painted containers became 11 more than ³₄ of the total number of containers. How many more containers were unpainted than painted on the first day?

	Painted	Not painted	Total
Before	3x4 = 12 u	10x4 = 40 u	13x4 = 52 u
Change	+ 389	- 389
After	12 u + 389	40 u - 389	52 u
Comparing painted and not painted containers in the end	3x13 + 11 = 39 u + 11	1x13 - 11 = 13 u - 11	4x13 = 52 u

30% = ³⁰₁₀₀ = ³₁₀
Painted : Not painted = 3 : 10

The total number of containers remains unchanged. Make the total number of containers at first and in the end the same.  LCM of 13 and 4 is 52.

The number of containers painted in the end is repeated.

39 u + 11 = 12 u + 389
39 u - 12 u = 389 - 11
27 u = 378

1 u = 378 ÷ 27 = 14

Number of more containers that were not painted than painted on the first day
= 40 u - 12 u
= 28 u
= 28 x 14
= 392

Answer(s): 392