The ratio of the number of biscuits in Container C to the number of biscuits in Container D was 7 : 5. 20% of the biscuits in Container C and 0.8 of those in Container D were cherry. After transferring the biscuits between the 2 boxes, the number of matcha biscuits in both boxes are the same. Likewise, the number of cherry biscuits in both boxes are the same. If a total of 252 biscuits were moved, how many more biscuits were there in Container C than Container D at first?

Container C		Container D
7 u		5 u
Cherry	Matcha	Cherry	Matcha
1.4 u	5.6 u	4 u	1 u
+ 1.3 u	- 2.3 u	- 1.3 u	+ 2.3 u
2.7 u	3.3 u	2.7 u	3.3 u

Number of cherry biscuits in Container C
= 20% x 7 u
= ²⁰₁₀₀ x 7 u
= 1.4 u

Number of matcha biscuits in Container C
= 7 u - 1.4 u
= 5.6 u

Number of cherry biscuits in Container D
= 0.8 x 5 u
= 4 u

Number of matcha biscuits in Container D
= 5 u - 4 u
= 1 u

Number of cherry biscuits in each box in the end
= (1.4 u + 4 u) ÷ 2
= 5.4 u ÷ 2
= 2.7 u

Number of matcha biscuits in each box in the end
= (5.6 u + 1 u) ÷ 2
= 6.6 u ÷ 2
= 3.3 u

Number of biscuits moved
= 1.3 u + 2.3 u
= 3.6 u

3.6 u = 252

1 u = 252 ÷ 3.6 = 70

Number of more biscuits in Container C than Container D at first
= 7 u - 5 u
= 2 u
= 2 x 70
= 140

Answer(s): 140