The ratio of the number of biscuits in Container Y to the number of biscuits in Container Z was 7 : 5. 40% of the biscuits in Container Y and 0.6 of those in Container Z were mango. After transferring the biscuits between the 2 boxes, the number of chocolate biscuits in both boxes are the same. Likewise, the number of mango biscuits in both boxes are the same. If a total of 252 biscuits were moved, how many more biscuits were there in Container Y than Container Z at first?

Container Y		Container Z
7 u		5 u
Mango	Chocolate	Mango	Chocolate
2.8 u	4.2 u	3 u	2 u
+ 0.1 u	- 1.1 u	- 0.1 u	+ 1.1 u
2.9 u	3.1 u	2.9 u	3.1 u

Number of mango biscuits in Container Y
= 40% x 7 u
= ⁴⁰₁₀₀ x 7 u
= 2.8 u

Number of chocolate biscuits in Container Y
= 7 u - 2.8 u
= 4.2 u

Number of mango biscuits in Container Z
= 0.6 x 5 u
= 3 u

Number of chocolate biscuits in Container Z
= 5 u - 3 u
= 2 u

Number of mango biscuits in each box in the end
= (2.8 u + 3 u) ÷ 2
= 5.8 u ÷ 2
= 2.9 u

Number of chocolate biscuits in each box in the end
= (4.2 u + 2 u) ÷ 2
= 6.2 u ÷ 2
= 3.1 u

Number of biscuits moved
= 0.1 u + 1.1 u
= 1.2 u

1.2 u = 252

1 u = 252 ÷ 1.2 = 210

Number of more biscuits in Container Y than Container Z at first
= 7 u - 5 u
= 2 u
= 2 x 210
= 420

Answer(s): 420