PSLE
There was a total of 19272 cm³ of water in rectangular tanks M and N at first. The height of the water level in tank N was 2 cm above that of tank M.

1. Find the height of the water level in tank M.
2. Betty poured 3300 cm³ of water out of tank N. Tank N was then half filled with water. What was the height of tank N?

(a)
Volume of water in Tank N with a height of 2 cm
= 30 x 22 x 2
= 1320 cm³

Volume of water in both tanks excluding the water that is 2 cm above that of Tank M
= 19272 - 1320
= 17952 cm³

Base area of Tank M
= 22 x 18
= 396 cm²

Base area of Tank N
= 30 x 22
= 660 cm²

Combined base areas of both tanks
= 396 + 660
= 1056 cm²

Height of water in Tank M 
= 17952 ÷ 1056
= 17 cm

(b)
Decrease in the height of Tank N after some water was poured out 
= 3300 ÷ 660
= 5 cm

Original height of water before some was poured out
= 17 + 2
= 19 cm

Height of water after some was poured out
= 19 - 5
= 14 cm

Height of Tank M
= 2 x 14
= 28 cm

Answer(s): (a) 17 cm; (b) 28 cm