Lesson 3 of 15
The biggest one they share
Show on a big screenRibbons of 12 m and 18 m. Cut equal pieces with nothing left over.
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Step 1 of 4
- Factors of 12: 1, 2, 3, 4, 6, 12.
- Factors of 18: 1, 2, 3, 6, 9, 18.
- Shared: 1, 2, 3, 6.
- Biggest shared factor: 6. HCF = 6.
The shared list has a top
A piece length must go into both 12 and 18. The longest such length is 6 m.
Both 12 and 18 share the factors 1, 2, 3 and 6. The biggest one is the highest common factor, or HCF.
HCF(12, 18) = 6 means: the HCF of 12 and 18 is 6.
Any two whole numbers share the factor 1. That is because 1 goes into every number. So HCF(8, 15) = 1.
Try the lab to finish this lesson.