Hose P and hose Q each fill an identical water tub at a constant rate. Hose P takes 40 minutes to fill the tub completely, while hose Q takes 60 minutes. The faster hose delivers 50 ml more water per minute than the slower hose.
- Which hose, P or Q, delivers water at the faster rate?
- What is the capacity of each tub in litres?
Need a hint?
Write both rates as the capacity divided by the time, then find their difference. Remember the answer must be in litres.
Worked answer
- (a) 40 minutes is less than 60 minutes, so hose P fills the tub faster and delivers water at the faster rate.
- (b) Let the capacity be C ml. Rate of P = C ÷ 40 and rate of Q = C ÷ 60.
- (b) Difference in rates: C ÷ 40 − C ÷ 60 = C ÷ 120 = 50 ml per minute.
- (b) So C = 50 × 120 = 6000 ml, which is 6 litres.
The mistake this question tests
Left out the units
Some pupils find C = 6000 and write 6000 litres, forgetting to change millilitres into litres.
How to fix it at home →Wrong answers children often give:
- 6000 Converting units (kg, ℓ, m, cm³)
More PSLE rate questions
Nurul bought 5 notebooks for $80
See the answer →MCQ · 2mA tap fills 3 litres of water in 45 seconds
See the answer →Structured · 3mAt a garden centre, 5 points are earned for every $4 spent
See the answer →Short answer · 2mKara notices that every 6 drops from the loose cap of her sports water bottle together make 5 ml of water
See the answer →Structured · 4mAt 8.00 a.m., a filling machine at Mrs Lim's drink stall began filling empty bottles
See the answer →Structured · 3mAt a community centre, a rectangular paddling pool measuring 120 cm by 60 cm by 40 cm was 3/4 full of water
See the answer →Practise PSLE rate until the mistakes stop.
Three PSLE questions, free, no sign-up. You’ll see exactly where the marks went. Then 7 days of everything for S$4.99.