Numbers up to 100
Primary 1 · Mathematics
Numbers up to 100
Lesson 7 of 7
13 min
Let's begin
At umuganda the people of the umudugudu clean the road.
Some carry stones. Some cut the long grass.
More neighbours keep arriving to help.
Every time, someone asks: how many now? Today you will answer that.
Read the story. Find the two numbers. Find the question.
Worked example
At umuganda, 32 people sweep the road. Then 15 more come to help.
More people came, so you put them together.
32 + 15 = 47
Ones: 2 + 5 = 7. Tens: 3 + 1 = 4 tens.
Now 47 people are working.
Worked example
Umutoni had 68 groundnuts. She gave 20 to her brother.
She gave some away, so you take away.
68 − 20 = 48
The ones stay 8. Tens: 6 − 2 = 4 tens.
Umutoni has 48 groundnuts left.
This one is not adding. Go slowly.
Worked example
Uwase has 45 beans. Mugisha has 23 beans.
How many more beans than Mugisha does Uwase have?
Match them up. Give each of Mugisha's 23 beans a partner from Uwase.
Some of Uwase's beans have no partner. Count those.
45 − 23 = 22
Uwase has 22 more beans than Mugisha.
Careful! The answer is not 68. That is what you get if you add.
Careful! The answer is not 45. That is only the bigger pile.
Tip
Read it, act it, write it
Lay out bundles and loose sticks. Act the story on the mat.
Did the pile grow? You add. Did the pile shrink? You take away.
Did the pile grow or shrink? Work the stories out.
Write the number sentence first. Then work it out.
Gatete picks 41 maize cobs. His sister picks 27. How many in all?
Answer: 68 cobs. Ones: 1 + 7 = 8. Tens: 4 + 2 = 6 tens.
Keza had 76 beans. She cooked 24 of them. How many are left?
Answer: 52 beans. Ones: 6 − 4 = 2. Tens: 7 − 2 = 5 tens.
Ishimwe has 58 stones. Mutesi has 35 stones. How many more than Mutesi does Ishimwe have?
Answer: 23 stones. 58 − 35 = 23. Take away, do not add.
43 people work at umuganda. 30 more come. How many now?
Answer: 73 people. The ones stay 3. Tens: 4 + 3 = 7 tens.
Umutoni counted 87 bottle caps. She gave 52 away. How many are left?
Answer: 35 caps. Ones: 7 − 2 = 5. Tens: 8 − 5 = 3 tens.
What you learned today
You can read every number up to 99 now, so go and find some. Start with Ni zingahe?, which is in Kinyarwanda and asks you on every page how many things you can see — free to read, from the Global Digital Library. Then read Ni iyihe nyamaswa yiruka cyane kuruta izindi?, also in Kinyarwanda and also free from the Global Digital Library: each page puts one more animal in the line, so you practise keeping a list in order, just as you did with 47, 49, 51, 74.
If you would like one in English, Zanele sees numbers from Book Dash is free to read too. Zanele spots numbers all around her: on doors, on buses, on the price list at the shop.
Then walk outside and find three numbers of your own. Say each one out loud, and say how many tens and how many ones it has.
Quick check
Gatete has 57 beans. Keza has 34. How many more has Gatete?
