LET’S TRY ONE
What is the greatest common factor of 12 and 18?
6
6 divides both numbers. No greater whole number is a factor of both.
Learning steps & teaching tips
Find the greatest whole-number factor shared by two positive integers.
- A common factor must divide both numbers exactly; choose the greatest one.
- Work through the example and explain why each operation is used.
- Estimate or use another method to check the result before choosing.
Try it together
Work with a partner: solve one example, explain the method, then change one number and predict what changes.
A common factor must divide both numbers exactly; choose the greatest one.