PSLE
There was a total of 25896 cm³ of water in rectangular tanks L and M at first. The height of the water level in tank M was 2 cm above that of tank L.

1. Find the height of the water level in tank L.
2. Sarah poured 6864 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 2 cm
= 33 x 26 x 2
= 1716 cm³

Volume of water in both tanks excluding the water that is 2 cm above that of Tank L
= 25896 - 1716
= 24180 cm³

Base area of Tank L
= 29 x 26
= 754 cm²

Base area of Tank M
= 33 x 26
= 858 cm²

Combined base areas of both tanks
= 754 + 858
= 1612 cm²

Height of water in Tank L 
= 24180 ÷ 1612
= 15 cm

(b)
Decrease in the height of Tank M after some water was poured out 
= 6864 ÷ 858
= 8 cm

Original height of water before some was poured out
= 15 + 2
= 17 cm

Height of water after some was poured out
= 17 - 8
= 9 cm

Height of Tank L
= 2 x 9
= 18 cm

Answer(s): (a) 15 cm; (b) 18 cm