Cylinder L and Cylinder M have a total amount of 1013 mℓ of water. For Cylinder M and Cylinder N, the total amount of water is 4220 mℓ. The amount of water in Cylinder L is ⁴₇ the amount of water in Cylinder N. What is the average amount of water in the 3 cylinders?
Cylinder L = 4 u
Cylinder N = 7 u 

Cylinder M + Cylinder L = 1013 --- (1)
Cylinder M + Cylinder N = 4220 --- (2)

(2) - (1)
(Cylinder M + Cylinder L) - (Cylinder M + Cylinder N) = 4220 - 1013
7 u - 4 u = 3207
3 u = 3207

1 u = 3207 ÷ 3 = 1069
Cylinder L = 4 u = 1069 x 4 = 4276

Cylinder L + Cylinder M + Cylinder N = 4276 + 4220 = 8496 mℓ

Average amount of water in the 3 cylinders
= 8496 ÷ 3 
= 2832 mℓ

Answer(s): 2832 mℓ