PSLE
At first, Containers X, Y and Z contained water as shown in Figure 1. Some water from X and Y was poured into Container Z without spilling. The amount of water left in Container X and Y is shown in Figure 2. What would be the amount of water in Container Z?
1 ℓ = 1000 mℓ

Container X 
10 intervals = 500
1 interval = 500 ÷ 10 = 50

Decrease in the volume of water in Container X
= 2 intervals of Container X
= 2 x 50
= 100 mℓ

Container Y
10 intervals = 200
1 interval = 200 ÷ 10 = 20

Decrease in the volume of water in Container Y
= 2 intervals of Container Y
= 2 x 20 
= 40 mℓ

Container Z
10 intervals = 1000
1 interval = 1000 ÷ 10 = 100

Volume of water in Container Z at first
= 6 intervals of Container Z
= 6 x 100
= 600 mℓ

Total decrease in volume of water in Containers X and Y
= 100 + 40
= 140 mℓ

Volume of water in Container Z in the end
= 600 + 140
= 740 mℓ

Answer(s): 740 mℓ