Cylinder Z and Cylinder A have a total amount of 834 mℓ of water. For Cylinder A and Cylinder B, the total amount of water is 4587 mℓ. The amount of water in Cylinder Z is ⁴₇ the amount of water in Cylinder B. What is the average amount of water in the 3 cylinders?
Cylinder Z = 4 u
Cylinder B = 7 u 

Cylinder A + Cylinder Z = 834 --- (1)
Cylinder A + Cylinder B = 4587 --- (2)

(2) - (1)
(Cylinder A + Cylinder Z) - (Cylinder A + Cylinder B) = 4587 - 834
7 u - 4 u = 3753
3 u = 3753

1 u = 3753 ÷ 3 = 1251
Cylinder Z = 4 u = 1251 x 4 = 5004

Cylinder Z + Cylinder A + Cylinder B = 5004 + 4587 = 9591 mℓ

Average amount of water in the 3 cylinders
= 9591 ÷ 3 
= 3197 mℓ

Answer(s): 3197 mℓ