PSLE
There was a total of 32812 cm³ of water in rectangular tanks E and F at first. The height of the water level in tank F was 7 cm above that of tank E.

1. Find the height of the water level in tank E.
2. Esther poured 7072 cm³ of water out of tank F. Tank F was then half filled with water. What was the height of tank F?

(a)
Volume of water in Tank F with a height of 7 cm
= 34 x 26 x 7
= 6188 cm³

Volume of water in both tanks excluding the water that is 7 cm above that of Tank E
= 32812 - 6188
= 26624 cm³

Base area of Tank E
= 30 x 26
= 780 cm²

Base area of Tank F
= 34 x 26
= 884 cm²

Combined base areas of both tanks
= 780 + 884
= 1664 cm²

Height of water in Tank E 
= 26624 ÷ 1664
= 16 cm

(b)
Decrease in the height of Tank F after some water was poured out 
= 7072 ÷ 884
= 8 cm

Original height of water before some was poured out
= 16 + 7
= 23 cm

Height of water after some was poured out
= 23 - 8
= 15 cm

Height of Tank E
= 2 x 15
= 30 cm

Answer(s): (a) 16 cm; (b) 30 cm