Cylinder R and Cylinder S have a total amount of 2894 mℓ of water. For Cylinder S and Cylinder T, the total amount of water is 3971 mℓ. The amount of water in Cylinder R is ²₅ the amount of water in Cylinder T. What is the average amount of water in the 3 cylinders?
Cylinder R = 2 u
Cylinder T = 5 u 

Cylinder S + Cylinder R = 2894 --- (1)
Cylinder S + Cylinder T = 3971 --- (2)

(2) - (1)
(Cylinder S + Cylinder R) - (Cylinder S + Cylinder T) = 3971 - 2894
5 u - 2 u = 1077
3 u = 1077

1 u = 1077 ÷ 3 = 359
Cylinder R = 2 u = 359 x 2 = 718

Cylinder R + Cylinder S + Cylinder T = 718 + 3971 = 4689 mℓ

Average amount of water in the 3 cylinders
= 4689 ÷ 3 
= 1563 mℓ

Answer(s): 1563 mℓ