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

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

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

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

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

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

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

Total decrease in volume of water in Containers N and P
= 150 + 80
= 230 mℓ

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

Answer(s): 630 mℓ