PSLE
There was a total of 15816 cm³ of water in rectangular tanks Y and Z at first. The height of the water level in tank Z was 3 cm above that of tank Y.

1. Find the height of the water level in tank Y.
2. Zoe poured 2880 cm³ of water out of tank Z. Tank Z was then half filled with water. What was the height of tank Z?

(a)
Volume of water in Tank Z with a height of 3 cm
= 30 x 24 x 3
= 2160 cm³

Volume of water in both tanks excluding the water that is 3 cm above that of Tank Y
= 15816 - 2160
= 13656 cm³

Base area of Tank Y
= 22 x 19
= 418 cm²

Base area of Tank Z
= 30 x 24
= 720 cm²

Combined base areas of both tanks
= 418 + 720
= 1138 cm²

Height of water in Tank Y 
= 13656 ÷ 1138
= 12 cm

(b)
Decrease in the height of Tank Z after some water was poured out 
= 2880 ÷ 720
= 4 cm

Original height of water before some was poured out
= 12 + 3
= 15 cm

Height of water after some was poured out
= 15 - 4
= 11 cm

Height of Tank Y
= 2 x 11
= 22 cm

Answer(s): (a) 12 cm; (b) 22 cm