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)
The lesson
You already know how to find 10 more or 10 less than a number. Three-digit numbers work the same way. You will also try jumps of 100.
Try 875. Add 100, and only the hundreds digit moves up, from 8 to 9, giving 975. Take away 100, and the hundreds digit moves down to 7, giving 775. The tens digit (7) and ones digit (5) do not change.
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.
Watch it
Where it sits
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.