Adding Three Small Numbers
Add three one-digit numbers using strategies including looking for pairs that make 10
What a learner can do afterwards
- Calculate 5 + 7 + 3 by first adding 7 + 3 = 10, then 5 + 10 = 15
- Add any three single-digit numbers correctly
- Identify useful pairs within three addends to make the calculation easier
The lesson
When you add three numbers, you can add them in any order. Look for two numbers that make 10. Add those two first. Then add the last number to 10. This turns a hard sum into an easy one.
Leo has 4 blocks, 6 blocks, and 8 blocks. He looks for a pair that makes 10 first. 4 and 6 make 10. Then he adds 8 more. 10 + 8 = 18. Leo has 18 blocks.
You can add numbers in any order. The total stays the same. Always look for a pair that makes 10 first. It makes adding three numbers much easier.
Find two numbers that make 10, add them first, then add the last number.
Watch it
Where it sits
Learn first
This opens up
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.