Elijah had three bags of potato starch, B, C and D and the mass of each bag of potato starch was in the ratio 4 : 5 : 4. Elijah decided to transfer 30% of potato starch from Bag B into Bag C and 80% of potato starch from Bag D into Bag C. Given that the mass of Bag C was 56.4 kg in the end, how many kilograms of potato starch were transferred into Bag C?

	B	C	D
Before	4 u	5 u	4 u
Change 1	- 1.2 u	+ 1.2 u
Change 2		+ 3.2 u	- 3.2 u
After	2.8 u	9.4 u	0.8 u

Mass of potato starch transferred from Bag B into Bag C
= 30% x 4 u
= ³⁰₁₀₀ x 4 u
= 2.8 u

Mass of potato starch transferred from Bag D into Bag C
= 80% x 4 u
= ⁸⁰₁₀₀ x 4 u
= 3.2 u

Mass of potato starch in Bag C in the end
= 5 u + 1.2 u + 3.2 u
= 9.4 u

9.4 u = 56.4 

1 u = 56.4 ÷ 9.4 = 6

Mass of potato starch transferred into Bag C
= 1.2 u + 3.2 u
= 4.4 u
= 4.4 x 6
= 26.4 kg

Answer(s): 26.4 kg