PSLE
There was a total of 13902 cm³ of water in rectangular tanks U and V at first. The height of the water level in tank V was 5 cm above that of tank U.

1. Find the height of the water level in tank U.
2. Yen poured 4263 cm³ of water out of tank V. Tank V was then half filled with water. What was the height of tank V?

(a)
Volume of water in Tank V with a height of 5 cm
= 29 x 21 x 5
= 3045 cm³

Volume of water in both tanks excluding the water that is 5 cm above that of Tank U
= 13902 - 3045
= 10857 cm³

Base area of Tank U
= 21 x 18
= 378 cm²

Base area of Tank V
= 29 x 21
= 609 cm²

Combined base areas of both tanks
= 378 + 609
= 987 cm²

Height of water in Tank U 
= 10857 ÷ 987
= 11 cm

(b)
Decrease in the height of Tank V after some water was poured out 
= 4263 ÷ 609
= 7 cm

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

Height of water after some was poured out
= 16 - 7
= 9 cm

Height of Tank U
= 2 x 9
= 18 cm

Answer(s): (a) 11 cm; (b) 18 cm