PSLE
There was a total of 26010 cm³ of water in rectangular tanks P and Q at first. The height of the water level in tank Q was 5 cm above that of tank P.

1. Find the height of the water level in tank P.
2. Kylie poured 6660 cm³ of water out of tank Q. Tank Q was then half filled with water. What was the height of tank Q?

(a)
Volume of water in Tank Q with a height of 5 cm
= 37 x 30 x 5
= 5550 cm³

Volume of water in both tanks excluding the water that is 5 cm above that of Tank P
= 26010 - 5550
= 20460 cm³

Base area of Tank P
= 30 x 25
= 750 cm²

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

Combined base areas of both tanks
= 750 + 1110
= 1860 cm²

Height of water in Tank P 
= 20460 ÷ 1860
= 11 cm

(b)
Decrease in the height of Tank Q after some water was poured out 
= 6660 ÷ 1110
= 6 cm

Original height of water before some was poured out
= 11 + 5
= 16 cm

Height of water after some was poured out
= 16 - 6
= 10 cm

Height of Tank P
= 2 x 10
= 20 cm

Answer(s): (a) 11 cm; (b) 20 cm