Numbers up to 20
Primary 1 · Mathematics
Numbers up to 20
Lesson 7 of 7
13 min
Let's begin
Keza and Uwase count beans on a mat at home.
Keza has more beans. Uwase wants to know how many more.
Nobody has written any numbers down yet.
Today you will turn a story into a number sentence.
Ishimwe has 8 bottle caps. Keza gives him 7 more.
The two groups come together, so you add.
Split 7 into 2 and 5. 8 + 2 = 10. 10 + 5 = 15.
8 + 7 = 15
Ishimwe has 15 bottle caps.
Always finish with the thing you counted, not just the number.
Worked example
Umutoni carries 16 mangoes to the market. She sells 9.
The mangoes leave her basket, so you take away.
Step 1 16 − 6 = 10. You have taken 6.
Step 2 3 more to take. 10 − 3 = 7.
16 − 9 = 7
Umutoni has 7 mangoes left.
Her answer is smaller than 16. That makes sense. She sold some.
Now back to the mat. Keza has 9 beans. Uwase has 4 beans.
How many more beans than Uwase does Keza have?
Lay the beans in two rows, one under the other.
Match 4 of Keza's beans to Uwase's 4 beans.
5 of Keza's beans have no partner.
9 − 4 = 5
So Keza has 5 more beans than Uwase.
Careful! More than does not mean add. If you answered 13, you put the rows together.
Careful! The answer is not 9 either. 9 is how many Keza has, not how many extra.
Tip
Read it, act it, write it
Use beans and act the story out on the floor.
Did the groups come together? Add. Did something go away? Take away.
For more than, match the two rows and count the ones left over.
Turn a story into a number sentence.
Do each one, then tap Show answer to check.
Uwase has 7 eggs. She buys 6 more. How many eggs now?
Answer: 13. Split 6 into 3 and 3. 7 + 3 = 10, then 10 + 3 = 13.
Mugisha had 14 pencils. He gave away 4. How many are left?
Answer: 10. Ones: 4 − 4 = 0, so only the ten is left.
Byiringiro has 11 sticks. Mutesi has 5 sticks. How many more sticks than Mutesi does Byiringiro have?
Answer: 6. Match 5 with 5. 11 − 5 = 6 sticks with no partner.
9 children play football. Then 8 more join them. How many children play?
Answer: 17. Split 8 into 1 and 7. 9 + 1 = 10, then 10 + 7 = 17.
Habimana picks 15 avocados. 6 of them fall in the grass and are lost. How many are left?
Answer: 9. Split 6 into 5 and 1. 15 − 5 = 10, then 10 − 1 = 9.
What you learned today
Read one of these with someone at home. Both are free to read from the Global Digital Library.
Ni zingahe? is in Kinyarwanda. The animals and birds ask you to count their things, so you answer how many on every page.
My Aunt Sells Fish is in easy English. An aunt sells fish at the market and says, let us count together.
Quick check
Gatete has 12 sticks. Mugisha has 5. How many more has Gatete?
