Numbers that share factors
Write the factors of 12 on one side of a page. Write the factors of 18 on the other side. Some numbers are in both lists.
Step 1 of 4
- Two circles: 12 and 18.
- 12's own factors: 4, 12.
- 18's own factors: 9, 18.
- Shared by both: 1, 2, 3, 6.
The rule
A common factor divides both numbers. Factors of 12: 1, 2, 3, 4, 6, 12. Factors of 18: 1, 2, 3, 6, 9, 18. 12 and 18 share four: 1, 2, 3, 6.
Watch out!
Any two numbers share the factor 1. So 7 and 15 share 1, and nothing more.
Two numbers that share only the factor 1 are co-prime. 7 and 15 are co-prime.
Why this matters
Why care? Share 12 laddoos and 18 barfis on plates. Every plate must get the same. The number of plates must divide both. So 6 plates work. Each plate gets 2 laddoos and 3 barfis.
Set the lab to 12 and 18. Then try 7 and 15.
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