The ratio of the number of wafers in Container R to the number of wafers in Container S was 7 : 3. 20% of the wafers in Container R and 0.6 of those in Container S were cherry. After transferring the wafers between the 2 containers, the number of mango wafers in both containers are the same. Likewise, the number of cherry wafers in both containers are the same. If a total of 240 wafers were moved, how many more wafers were there in Container R than Container S at first?

Container R		Container S
7 u		3 u
Cherry	Mango	Cherry	Mango
1.4 u	5.6 u	1.8 u	1.2 u
+ 0.2 u	- 2.2 u	- 0.2 u	+ 2.2 u
1.6 u	3.4 u	1.6 u	3.4 u

Number of cherry wafers in Container R
= 20% x 7 u
= ²⁰₁₀₀ x 7 u
= 1.4 u

Number of mango wafers in Container R
= 7 u - 1.4 u
= 5.6 u

Number of cherry wafers in Container S
= 0.6 x 3 u
= 1.8 u

Number of mango wafers in Container S
= 3 u - 1.8 u
= 1.2 u

Number of cherry wafers in each container in the end
= (1.4 u + 1.8 u) ÷ 2
= 3.2 u ÷ 2
= 1.6 u

Number of mango wafers in each container in the end
= (5.6 u + 1.2 u) ÷ 2
= 6.8 u ÷ 2
= 3.4 u

Number of wafers moved
= 0.2 u + 2.2 u
= 2.4 u

2.4 u = 240

1 u = 240 ÷ 2.4 = 100

Number of more wafers in Container R than Container S at first
= 7 u - 3 u
= 4 u
= 4 x 100
= 400

Answer(s): 400