Grade
3

Guess My Rule: Three-Digit Numbers

What are the rules for the circles?

In the red circle: 325, 295, 340, 258, 261, and 255. In the blue circle: 248, 245, and 249. In the intersection of the red and blue circles: 251, 253, and 254. Outside the circles: 355, 242, and 359.
  1. What's the lowest number in each circle? What's the greatest number in each circle?
    What do you notice about the range of numbers?
  2. Some numbers belong in the circles, and some do not.
    What is the rule to be in the red circle? What is the rule to be in the blue circle?
    What is the rule to be in both circles?
  3. Write at least one more number that belongs only in the red circle.
  4. Write at least one more number that belongs only in the blue circle.
  5. Where would you place the number 250? Why?

Round each number to the nearest ten and the nearest hundred. What do you notice about the numbers in the circles after you round them?

Make your own rules about rounded numbers. You can use the circles below or draw your own.

If possible, show some examples that belong inside each circle and some examples that don’t belong in either circle.

blank red and blue circles that overlap, with text, 'The rule for the red circle is:' and 'The rule for the blue circle is:'
Printable Version

Google doc for printing and copying

Reference for Educators

Sample problems and solutions