Xavier had three bags of corn starch, Q, R and S and the mass of each bag of corn starch was in the ratio 4 : 1 : 4. Xavier decided to transfer 40% of corn starch from Bag Q into Bag R and 80% of corn starch from Bag S into Bag R. Given that the mass of Bag R was 29 kg in the end, how many kilograms of corn starch were transferred into Bag R?

	Q	R	S
Before	4 u	1 u	4 u
Change 1	- 1.6 u	+ 1.6 u
Change 2		+ 3.2 u	- 3.2 u
After	2.4 u	5.8 u	0.8 u

Mass of corn starch transferred from Bag Q into Bag R
= 40% x 4 u
= ⁴⁰₁₀₀ x 4 u
= 2.4 u

Mass of corn starch transferred from Bag S into Bag R
= 80% x 4 u
= ⁸⁰₁₀₀ x 4 u
= 3.2 u

Mass of corn starch in Bag R in the end
= 1 u + 1.6 u + 3.2 u
= 5.8 u

5.8 u = 29 

1 u = 29 ÷ 5.8 = 5

Mass of corn starch transferred into Bag R
= 1.6 u + 3.2 u
= 4.8 u
= 4.8 x 5
= 24 kg

Answer(s): 24 kg