Number Patterns
Primary 1 · Mathematics
Number Patterns
Lesson 3 of 4
12 min
Let's begin
Umutoni holds 20 beans in her hand.
Each day she plants 2 beans behind the house.
Her hand gets lighter and lighter. Today you will count down with her.
Look at the numbers. Are they getting bigger or smaller?
Umutoni's beans go 20, 18, 16, ___
They are getting smaller. This pattern takes away.
| Day | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| Beans left | 20 | 18 | 16 | ? |
From 20 to 18 you take away 2. From 18 to 16 you take away 2.
The step is take away 2.
16 take away 2 is 14.
Careful! Some children say 18. They found the step but went back up. Some say 15. They took away only 1.
Gatete has 50 Frw in coins. He spends 10 Frw each day.
His money goes 50, 40, 30, 20, 10.
The step is take away 10. Only the tens digit changes.
Worked example
30, 25, 20, ___.
Step 1 Which way? The numbers are getting smaller.
Step 2 Find the step. From 30 to 25 you take away 5.
Step 3 Take the step off the last number. 20 take away 5 is 15.
Is 15 right? Put the step back on. 15 and 5 more make 20.
You landed on the number you started from. Your answer is good.
Byiringiro has 12 avocados on his tray. He sells 2 at a time.
His tray goes 12, 10, 8, ___
The numbers are getting smaller. Keep them going down.
8 take away 2 is 6.
Careful! Some children say 10 here. They turned the pattern around and went back up the way they came.
Tip
Going down? Take the step away
First say it: the numbers are getting smaller.
Then say the step: take away 2. Say it every single time.
A cat spends her money: count back by 2, 5 and 10.
Say the direction, then the step. Then tap Show answer to check.
10, 9, 8, 7, ___
Answer: 6. Smaller. The step is take away 1.
16, 14, 12, ___
Answer: 10. Smaller. The step is take away 2.
40, 30, 20, ___
Answer: 10. Smaller. The step is take away 10.
Keza had 25 mangoes. She sells 5 at each stall: 25, 20, 15, ___
Answer: 10. The step is take away 5. 15 take away 5 is 10.
Is 18, 21, 24 a counting-down pattern?
Answer: no. The numbers are getting bigger. That pattern adds 3.
What you learned today
Quick check
