PSLE
There was a total of 11550 cm³ of water in rectangular tanks S and T at first. The height of the water level in tank T was 4 cm above that of tank S.

1. Find the height of the water level in tank S.
2. Shannon poured 2250 cm³ of water out of tank T. Tank T was then half filled with water. What was the height of tank T?

(a)
Volume of water in Tank T with a height of 4 cm
= 25 x 18 x 4
= 1800 cm³

Volume of water in both tanks excluding the water that is 4 cm above that of Tank S
= 11550 - 1800
= 9750 cm³

Base area of Tank S
= 20 x 15
= 300 cm²

Base area of Tank T
= 25 x 18
= 450 cm²

Combined base areas of both tanks
= 300 + 450
= 750 cm²

Height of water in Tank S 
= 9750 ÷ 750
= 13 cm

(b)
Decrease in the height of Tank T after some water was poured out 
= 2250 ÷ 450
= 5 cm

Original height of water before some was poured out
= 13 + 4
= 17 cm

Height of water after some was poured out
= 17 - 5
= 12 cm

Height of Tank S
= 2 x 12
= 24 cm

Answer(s): (a) 13 cm; (b) 24 cm