Adding numbers
Add up to four two-digit numbers using strategies based on place value and properties of operations
What a learner can do afterwards
- Add three or four two-digit numbers by grouping tens and ones
- Look for pairs that make multiples of 10 to simplify addition
- Explain the strategy used to combine multiple addends
The lesson
Sometimes you need to add three or four two-digit numbers, like 14 + 23 + 32 + 19. Adding them one at a time from left to right works, but it gets confusing fast. A better way is to split each number into its tens and ones. Add all the tens together, then add all the ones together. Last, add those two totals to get your answer.
Mia adds 14 + 23 + 32 + 19. First she adds the tens: 10 + 20 + 30 + 10 = 70. Then she adds the ones: 4 + 3 + 2 + 9 = 18. Last, she adds those two totals: 70 + 18 = 88.
Before you add everything in order, scan the ones digits for a pair that makes 10. For example, 16 and 24 have ones digits 6 and 4, and 6 + 4 = 10. So 16 + 24 = 40 exactly. Pairing numbers like this first can make the whole sum easier.
Split into tens and ones, add each group, then combine, and look for pairs that make ten along the way.
Watch it
Where it sits
This opens up
Nothing builds on it yet.
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.