PSLE
There was a total of 34170 cm³ of water in rectangular tanks X and Y at first. The height of the water level in tank Y was 2 cm above that of tank X.

1. Find the height of the water level in tank X.
2. Tiffany poured 3330 cm³ of water out of tank Y. Tank Y was then half filled with water. What was the height of tank Y?

(a)
Volume of water in Tank Y with a height of 2 cm
= 37 x 30 x 2
= 2220 cm³

Volume of water in both tanks excluding the water that is 2 cm above that of Tank X
= 34170 - 2220
= 31950 cm³

Base area of Tank X
= 34 x 30
= 1020 cm²

Base area of Tank Y
= 37 x 30
= 1110 cm²

Combined base areas of both tanks
= 1020 + 1110
= 2130 cm²

Height of water in Tank X 
= 31950 ÷ 2130
= 15 cm

(b)
Decrease in the height of Tank Y after some water was poured out 
= 3330 ÷ 1110
= 3 cm

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

Height of water after some was poured out
= 17 - 3
= 14 cm

Height of Tank X
= 2 x 14
= 28 cm

Answer(s): (a) 15 cm; (b) 28 cm