10 or 100 More or Less
Find 10 or 100 more or less than a given number up to 1000
What a learner can do afterwards
- Given a three-digit number, state what is 10 more and 10 less
- Given a three-digit number, state what is 100 more and 100 less
- Explain the strategy using place-value understanding (e.g. only the tens/hundreds digit changes)
1 · Read
Three-digit numbers use the same place value idea. A jump of 10 changes the tens digit. A jump of 100 changes the hundreds digit.
Try 739. Add 100, and only the hundreds digit moves up, from 7 to 8, giving 839. Take away 100, and the hundreds digit moves down to 6, giving 639. The tens digit (3) and ones digit (9) do not change. For a two-step change, try 701. First add 10 to make 711. Then take away 100 from 711 to make 611. The first jump changes the tens digit, and the second changes the hundreds digit.
Look at which digit is supposed to move. A jump of 10 moves the tens digit. A jump of 100 moves the hundreds digit. Every other digit stays put.
Adding or taking 10 moves the tens digit, and adding or taking 100 moves the hundreds digit, while every other digit stays the same.
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2 · Watch
Take it off screen
Where it sits
Where this leads
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