PSLE
There was a total of 20070 cm³ of water in rectangular tanks J and K at first. The height of the water level in tank K was 3 cm above that of tank J.

1. Find the height of the water level in tank J.
2. Zoe poured 3960 cm³ of water out of tank K. Tank K was then half filled with water. What was the height of tank K?

(a)
Volume of water in Tank K with a height of 3 cm
= 30 x 22 x 3
= 1980 cm³

Volume of water in both tanks excluding the water that is 3 cm above that of Tank J
= 20070 - 1980
= 18090 cm³

Base area of Tank J
= 26 x 21
= 546 cm²

Base area of Tank K
= 30 x 22
= 660 cm²

Combined base areas of both tanks
= 546 + 660
= 1206 cm²

Height of water in Tank J 
= 18090 ÷ 1206
= 15 cm

(b)
Decrease in the height of Tank K after some water was poured out 
= 3960 ÷ 660
= 6 cm

Original height of water before some was poured out
= 15 + 3
= 18 cm

Height of water after some was poured out
= 18 - 6
= 12 cm

Height of Tank J
= 2 x 12
= 24 cm

Answer(s): (a) 15 cm; (b) 24 cm