Billy had three bags of potato starch, V, W and X and the mass of each bag of potato starch was in the ratio 4 : 1 : 3. Billy decided to transfer 30% of potato starch from Bag V into Bag W and 90% of potato starch from Bag X into Bag W. Given that the mass of Bag W was 24.5 kg in the end, how many kilograms of potato starch were transferred into Bag W?

	V	W	X
Before	4 u	1 u	3 u
Change 1	- 1.2 u	+ 1.2 u
Change 2		+ 2.7 u	- 2.7 u
After	2.8 u	4.9 u	0.3 u

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

Mass of potato starch transferred from Bag X into Bag W
= 90% x 3 u
= ⁹⁰₁₀₀ x 3 u
= 2.7 u

Mass of potato starch in Bag W in the end
= 1 u + 1.2 u + 2.7 u
= 4.9 u

4.9 u = 24.5 

1 u = 24.5 ÷ 4.9 = 5

Mass of potato starch transferred into Bag W
= 1.2 u + 2.7 u
= 3.9 u
= 3.9 x 5
= 19.5 kg

Answer(s): 19.5 kg