Primary 5 · Number & Algebra

P5 rate

A rate tells you how much of one thing you get for each unit of another, such as litres per minute or dollars per kilogram. In P5, your child uses a rate to find a total, a number of units or the rate itself. Most lost marks come from the units, before any multiplying starts.

Taught in
Term 3
Syllabus
2 skills
Usual slip
Leaves the hour out

A tap filling 4.5 litres per minute

What your child learns in P5 rate

Two skills, each with what it looks like on a worksheet.

Follows the latest (2026) MOE syllabus
See the syllabus wording
  • rate as the amount of a quantity per unit of another quantity
  • finding rate, total amount or number of units given the other two quantities

What "per" means

A rate is an amount for each one unit of something else, like litres per minute or dollars per kilogram. "Per" means "for each". Know the amount for 1 unit, and you can find it for any number of units.

MinutesLitres
14.5
29
1045
4.5 litres for each minute

Any two give the third

A rate question links three things: the rate, the number of units and the total amount. Know two and you can find the third. Multiply for the total. Divide the total to find either of the others.

To findWorking
Total amount$3 × 4 = $12
Number of units$12 ÷ $3 per kg = 4 kg
Rate$12 ÷ 4 = $3 per kg
Rice at $3 per kg, so 4 kg cost $12

Key facts and formulas

Term 3
  • Ratetotal÷number of units\text{total} \div \text{number of units}The amount for 1 unit.Example$42 for 6 kg → 42÷6=42 \div 6 = $7\text{\textdollar}7
  • Total amountrate×number of units\text{rate} \times \text{number of units}Example9 kg → 7×9=7 \times 9 = $63\text{\textdollar}63
  • Number of unitstotal÷rate\text{total} \div \text{rate}Example$35 → 35÷7=35 \div 7 = 5 kg5\,\text{kg}

Words to know

Rate
How much of one quantity for each unit of another, such as 4.5 litres per minute.
Per
For each. "$3 per kg" means $3 for each kilogram.
Total amount
The whole quantity, such as all the water that flows in or the whole price paid.
Number of units
How many minutes, kilograms or hours the rate is counted over.
Convert
Change a quantity into another unit, such as 1 h 20 min into 80 minutes.

The sentence that costs the mark

A tap fills a tank at 4.5 litres per minute. How much water flows in 1 h 20 min?

What the working usually does

4.5 litres ×20 minutes=90 litres

Multiplies by the minutes printed on the clock and leaves the hour out.

What the question asked

4.5 litres ×80 minutes=360 litres

Turns the whole time into minutes first, because the rate is per minute.

Both are one clean multiplication and both give a believable tankful. Neither has an arithmetic error in it. The time went wrong before any multiplying started.

The same P5 rate question, worked properly

Lah works through it the way she does every question in StudyLah: one step at a time, marking the picture as she goes.

A tap drips at a rate of 8 mℓ per second. How much water will drip from it in 3 minutes?

Step 1 of 5▌
  1. The rate is 8 mℓ per second, but the time is in minutes. So change the minutes into seconds before multiplying.
  2. Each minute is 60 seconds, so 3 minutes = 3 × 60 = 180 seconds.
  3. Now 8 mℓ drips in each of the 180 seconds: 180 × 8 = 1440 mℓ.
  4. Multiplying by 3 instead gives only 24 mℓ. That is just 3 seconds of dripping, far too little for 3 minutes.
  5. So 1440 mℓ of water drips from the tap in 3 minutes.

Every question in StudyLah comes with a walkthrough like this one.

Try it free

Three quick P5 rate questions

Try them together, then tap to check.

Question 1

Daniel worked 5 hours a day for 4 days. He was paid $280 in total at the same rate. How much was he paid for one hour?

Show answer

Answer$14. He worked 5 × 4 = 20 hours, so 1 hour paid $280 ÷ 20 = $14.

Question 2

A conveyor belt packs 15 parcels each minute. At the same rate, how many minutes will it take to pack 270 parcels?

Show answer

Answer18 minutes. Each minute packs 15 parcels, so 270 ÷ 15 = 18.

Question 3

A drink stall sells 40 cups in 30 minutes. If sales continue at the same rate, how many cups are sold in 3 hours?

Show answer

Answer240 cups. 3 hours is 180 minutes, which is 6 lots of 30 minutes, and 6 × 40 = 240.

Helping at home

How to tell it has clicked

You do not need to do the maths to check this. When a rate turns up, ask one thing: "per what?"

Then look at whether the time or the mass in the question is in that same unit. A child who converts before multiplying has understood it. A child who multiplies the numbers in the order they appear has not, and the answer still looks tidy.

Try this tonight

Next time you fill a water bottle, time ten seconds of it and work out the rate per second together. Then ask how long the whole two-litre bottle would take.

The second question forces the unit check, which is the thing being tested. It takes a minute at the sink and needs no worksheet.

Before and after P5 rate

  1. Builds on

    Primary 3 Time

    Finds durations and reads the 24-hour clock

  2. You are here

    Primary 5 Rate

    Uses an amount per unit to find totals

The methods your child will use here

More in Primary 5

Struggling with the working rather than the topic itself? How to help your child with problem sums

See how your child is doing on this topic

StudyLah marks each step separately, so you can see whether it was the setup or the arithmetic that cost the mark.

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