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

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

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

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

Decrease in the volume of water in Container Q
= 3 intervals of Container Q
= 3 x 20 
= 60 mℓ

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

Volume of water in Container R at first
= 5 intervals of Container R
= 5 x 100
= 500 mℓ

Total decrease in volume of water in Containers P and Q
= 100 + 60
= 160 mℓ

Volume of water in Container R in the end
= 500 + 160
= 660 mℓ

Answer(s): 660 mℓ