PSLE
There was a total of 9974 cm³ of water in rectangular tanks D and E at first. The height of the water level in tank E was 4 cm above that of tank D.

1. Find the height of the water level in tank D.
2. Hilda poured 3094 cm³ of water out of tank E. Tank E was then half filled with water. What was the height of tank E?

(a)
Volume of water in Tank E with a height of 4 cm
= 26 x 17 x 4
= 1768 cm³

Volume of water in both tanks excluding the water that is 4 cm above that of Tank D
= 9974 - 1768
= 8206 cm³

Base area of Tank D
= 19 x 16
= 304 cm²

Base area of Tank E
= 26 x 17
= 442 cm²

Combined base areas of both tanks
= 304 + 442
= 746 cm²

Height of water in Tank D 
= 8206 ÷ 746
= 11 cm

(b)
Decrease in the height of Tank E after some water was poured out 
= 3094 ÷ 442
= 7 cm

Original height of water before some was poured out
= 11 + 4
= 15 cm

Height of water after some was poured out
= 15 - 7
= 8 cm

Height of Tank D
= 2 x 8
= 16 cm

Answer(s): (a) 11 cm; (b) 16 cm