The ratio of the number of puffs in Container K to the number of puffs in Container L was 7 : 5. 20% of the puffs in Container K and 0.6 of those in Container L were strawberry. After transferring the puffs between the 2 boxes, the number of vanilla puffs in both boxes are the same. Likewise, the number of strawberry puffs in both boxes are the same. If a total of 156 puffs were moved, how many more puffs were there in Container K than Container L at first?

Container K		Container L
7 u		5 u
Strawberry	Vanilla	Strawberry	Vanilla
1.4 u	5.6 u	3 u	2 u
+ 0.8 u	- 1.8 u	- 0.8 u	+ 1.8 u
2.2 u	3.8 u	2.2 u	3.8 u

Number of strawberry puffs in Container K
= 20% x 7 u
= ²⁰₁₀₀ x 7 u
= 1.4 u

Number of vanilla puffs in Container K
= 7 u - 1.4 u
= 5.6 u

Number of strawberry puffs in Container L
= 0.6 x 5 u
= 3 u

Number of vanilla puffs in Container L
= 5 u - 3 u
= 2 u

Number of strawberry puffs in each box in the end
= (1.4 u + 3 u) ÷ 2
= 4.4 u ÷ 2
= 2.2 u

Number of vanilla puffs in each box in the end
= (5.6 u + 2 u) ÷ 2
= 7.6 u ÷ 2
= 3.8 u

Number of puffs moved
= 0.8 u + 1.8 u
= 2.6 u

2.6 u = 156

1 u = 156 ÷ 2.6 = 60

Number of more puffs in Container K than Container L at first
= 7 u - 5 u
= 2 u
= 2 x 60
= 120

Answer(s): 120