Measuring and Money
Primary 3 · Mathematics
Measuring and Money
Lesson 3 of 3
13 min
Let's begin
Keza's mother folds a 1000 Frw note into her hand. Bring bread and milk, she says.
At the shop the bread costs 350 Frw and the milk costs 250 Frw. Keza stares at the note. Will it be enough? And how much money should the shopkeeper give back?
Let's go shopping together and work it out.
In Rwanda we pay in Rwandan francs. We write them as Frw.
Some money is coins: 1, 5, 10, 20, 50 and 100 Frw.
Some money is notes: 500, 1000, 2000 and 5000 Frw.
A bigger number means the money is worth more. A 1000 Frw note is worth the same as two 500 Frw notes.
Worked example
How many 100 Frw coins do you need to make 500 Frw?
Count up in hundreds: 100, 200, 300, 400, 500.
You counted 5 times, so you need 5 coins.
Worked example
Bread costs 350 Frw. Milk costs 250 Frw. What is the total?
Split each price into hundreds, tens and ones.
Ones: 0 + 0 = 0.
Tens: 50 + 50 = 100. Look — the tens have made a whole extra hundred! Carry it over.
Hundreds: 300 + 200 = 500, and the carried 100 makes 600.
The total is 600 Frw.
You can check it another way: 350 + 200 = 550, then 550 + 50 = 600. Same answer. Good.
Change is the money the shopkeeper gives back to you. You get change when you hand over more than the price.
Worked example
Keza's shopping cost 600 Frw. She pays with a 1000 Frw note. What change should she get?
The easy way is to count up from the price to the note.
Start at 600. How much more do you need to reach 1000?
600 + 400 = 1000.
So the change is 400 Frw.
Check by taking away: 1000 − 600 = 400. It matches.
Worked example
Gatete buys a pen for 250 Frw and pays with a 1000 Frw note.
Count up from 250. First get to a round hundred: 250 + 50 = 300.
Now from 300 up to 1000: 300 + 700 = 1000.
Add the two jumps: 50 + 700 = 750 Frw change.
Careful! The change is not 250 Frw. The 250 Frw is what the pen cost — it is not what comes back.
Worked example
Mugisha buys 3 exercise books. Each one costs 200 Frw.
Count on in 200s: 200, 400, 600.
The books cost 600 Frw altogether. That is the same as 3 times 200.
Worked example
Ishimwe has 1000 Frw. Avocados cost 200 Frw each. How many can he buy?
Count up in 200s until you reach 1000: 200, 400, 600, 800, 1000.
That is 5 jumps, so he can buy 5 avocados — and he will have nothing left over.
Worked example
Umutoni has 800 Frw. She wants soap for 600 Frw and salt for 300 Frw.
Step 1 Add the prices: 600 + 300 = 900 Frw.
Step 2 Compare with her money: 900 Frw is more than 800 Frw.
So she does not have enough.
Step 3 How much is she short? 900 - 800 = 100 Frw. She needs 100 Frw more.
Tip
Two words to keep apart
Total = what you must pay. Add the prices together.
Change = what the shopkeeper hands back. Take the total away from the money you gave.
The easiest trick for change: start at the total and count up to the note you paid with. Whatever you counted along the way is the change.
Do each one on paper, then tap Show answer to check.
What you learned today
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