PSLE
There was a total of 20610 cm³ of water in rectangular tanks L and M at first. The height of the water level in tank M was 3 cm above that of tank L.

1. Find the height of the water level in tank L.
2. Gem poured 5600 cm³ of water out of tank M. Tank M was then half filled with water. What was the height of tank M?

(a)
Volume of water in Tank M with a height of 3 cm
= 32 x 25 x 3
= 2400 cm³

Volume of water in both tanks excluding the water that is 3 cm above that of Tank L
= 20610 - 2400
= 18210 cm³

Base area of Tank L
= 23 x 18
= 414 cm²

Base area of Tank M
= 32 x 25
= 800 cm²

Combined base areas of both tanks
= 414 + 800
= 1214 cm²

Height of water in Tank L 
= 18210 ÷ 1214
= 15 cm

(b)
Decrease in the height of Tank M after some water was poured out 
= 5600 ÷ 800
= 7 cm

Original height of water before some was poured out
= 15 + 3
= 18 cm

Height of water after some was poured out
= 18 - 7
= 11 cm

Height of Tank L
= 2 x 11
= 22 cm

Answer(s): (a) 15 cm; (b) 22 cm