Review: Think in Tens and Ones
Build, compare, and change two-digit numbers using groups of ten.
Bring the unit skills together
Use these 4 new cases to check your reasoning. Choices are temporary and are not saved to an account, sent to staff or recorded as school grades. Download your current review choices before leaving or reloading.
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Use the skills in a new task
Make a pretend dot-storage plan on paper. Shelf A has 32 dots stored as tens and ones; shelf B has 28. Draw or describe each shelf and compare them. Add one ten-box to A. On a separate shelf with 70 dots in ten-boxes, remove 20 dots. Show an addition check for that subtraction.
Work on paper or in your own document. Explain the choices you made.
- Represent 32 as three tens and two ones, and 28 as two tens and eight ones.
- Explain that 32 > 28 by comparing tens.
- Find 32 + 10 = 42 with the two ones unchanged.
- Find 70 − 20 = 50 and check 50 + 20 = 70.
Compare with a model response
A has 3 tens and 2 ones; B has 2 tens and 8 ones. A has more because three tens is more than two. Adding one ten to A gives 42. Seven tens minus two tens leaves five tens: 70 − 20 = 50, and 50 + 20 = 70.
A different response can also meet the criteria. Compare the evidence and reasoning, rather than copying the wording.