The figure is not drawn to scale. Tank P measuring 50 cm by 45 cm by 20 cm contained 12.9 ℓ of water. Tank Q measuring 42 cm by 25 cm by 32 cm contained 21 ℓ of water. Ivan poured some water from Tank P into Tank Q without spilling and the water level of Tank Q rose to 28 cm. What was the height of water level left in Tank P?
1 ℓ = 1000 cm³
21 ℓ = 21000 cm³
12.9 ℓ = 12.9 x 1000 = 12900 cm³

Height of water in Tank Q at first
= 21000 ÷ 42 ÷ 25
= 20 cm

Increase in the height of water in Tank Q
= 28 - 20
= 8 cm

Volume of water poured into Tank Q
= 42 x 25 x 8
= 8400 cm³ 

Volume of water left in Tank P
= 12900 - 8400
= 4500 cm³ 

Height of water left in Tank P
= 4500 ÷ 50 ÷ 45
= 2 cm

Answer(s): 2 cm