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

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

Decrease in the volume of water in Container Q
= 3 intervals of Container Q
= 3 x 50
= 150 mℓ

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

Decrease in the volume of water in Container R
= 4 intervals of Container R
= 4 x 20 
= 80 mℓ

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

Volume of water in Container S at first
= 4 intervals of Container S
= 4 x 100
= 400 mℓ

Total decrease in volume of water in Containers Q and R
= 150 + 80
= 230 mℓ

Volume of water in Container S in the end
= 400 + 230
= 630 mℓ

Answer(s): 630 mℓ