Unit 3, Lesson 16
Round and Round Again
Grade 3
Activity 1
All the Numbers
- What are all the whole numbers that would round to 50 if you're rounding to the nearest ten? You can use this number line if it helps you.
- What are all the whole numbers that would round to 70 if you're rounding to the nearest ten?
- What are all the whole numbers that would round to 600 if you're rounding to the nearest hundred?
If you finish early, find the whole numbers that would round to 100 and to 500 if you’re rounding to the nearest hundred. Compare your lists with a partner's lists and discuss the patterns you see to.
Activity 2
What’s My Mystery Number?
Write down a number between 100 and 1,000 on your index card. This is your mystery number.
Fold your index card in half so that no one can see your mystery number.
Write 3 clues about your mystery number by finishing these sentences:
- My mystery number is (odd or even) _____.
- My mystery number rounds to _____.
- My mystery number is between _____ and _____.
Play What’s My Number?
- Read the clues for your mystery number.
- Starting with the person on your right, have every member in your team try to guess your mystery number and explain their reasoning.
- If they haven’t guessed the mystery number by the time the last person shares, reveal the mystery number.
- Repeat Steps 1-3 with the next person in the group reading the clues for their mystery number.
Student Section Summary
We learned that rounding is a formal way to decide what number is closest to a given number. We rounded numbers to the nearest ten and the nearest hundred. We saw that a number line can help us see the closest multiple of 10 or multiple of 100.
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