A shop sells identical notebooks. 4 notebooks cost $12. How much does 1 notebook cost?
The rate is $3 per notebook.
Ans: $3
Example 1
A hose sprays 360 ml of water in 3 minutes. How much water sprays out in 1 second?
2 ml per second
Ans: 2
How to solve it
Draw one bar for the whole, 12 dollars, and cut it into 4 equal units, one for each notebook.
Share the total over the units: 12 divided by 4 is 3, so 1 notebook costs 3 dollars.
Say it as a rate: 3 dollars per notebook. To find the amount for each one, divide the total by the number of ones.
Make the units match the question: 3 minutes is 180 seconds, so 1 second gets 360 divided by 180, which is 2 millilitres.
Name the one you are asked for. For each second, the rate is 2 millilitres per second.
A rate is an amount for each one. Cut the total into as many equal units as there are ones. One unit is the rate. And name the one. Each notebook, each minute, each second. The one you name decides the rate.
Practice questions with worked solutions
Question 1 is free to try. The other 6 open in the free trial, each with its full working.
This page teaches rate as the amount of one quantity per unit of another, the first Primary 5 outcome in the Rate strand.
What your child learns here
This page teaches rate as the amount of one quantity per unit of another, the first Primary 5 outcome in the Rate strand. Your child shares a total over the number of units and writes the rate with both units, such as $3 per kg.
A rate names two quantities: dollars per kilogram, litres per minute, pages per day.
To find a rate, divide the total by the number of units.
The unit after 'per' may be a step such as each 100 g, rather than a single unit.
Units must match the question: litres per hour may need to become millilitres per hour.
Does the answer make sense?
The amount for one unit must be smaller than the total for several, because the total has been shared out. So your child's price for one notebook must be less than the price of four, and an answer changed into a smaller unit, such as litres into millilitres, will show a bigger number.
How to practise these questions
Basic questions train reading a rate as the amount for each one unit, whether per day, per item or per length. Intermediate questions add converting the total into the unit the answer needs before sharing it. Challenge questions require counting the units first, or finding one part of a mixed total, before the rate can be worked out. When the per-unit step is unclear, watch that question's solution film and redo it later from Revision.
Questions parents ask
What does per mean in maths? Per means for each. A rate of $2 per kg is $2 for each kilogram.
Is rate per unit in the Primary 5 syllabus? Yes. The first Primary 5 Rate outcome is rate as the amount of a quantity per unit of another quantity.
How do I explain rate to my child? Start with a price label: the cost for one item or one kilogram is a rate. Then ask what 3 of them would cost, and what one costs if 3 cost a given amount.
