GCF for 9, 15 and 18

"Greatest Common Factor of 3 Numbers" Calculator
Greatest Common Factor of
,
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What's the Greatest Common Factor (GCF) of 9, 15 and 18?

Answer

GCF of 9, 15 and 18 is
3

Common factors: 1, 3

3 divides all three: 9 ÷ 3 = 3, 15 ÷ 3 = 5, 18 ÷ 3 = 6 — and 3, 5 and 6 have no factor but 1 common to all of them, so no larger number divides all three.

9 = 32

15 = 3 × 5

18 = 2 × 32

Prime91518Lowest power
2——2—
3323323
5—5——

— = power 0: the prime is not a factor of this number, so it cannot be in the GCF.

GCF = 3

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GCF Table

1st2nd3rdGCF
39153
49151
59151
69153
79151
89151
99153
910151
911151
912153
913151
914151
915153
915161
915171
915183
915191
915201
915213
915221
915231
915243
915251
915261
915273
915281
915291
915303
915311
915321

FAQ

What's the Greatest Common Factor (GCF) of 9, 15 and 18?

GCF of 9, 15 and 18 is 3

What prime factors do 9, 15 and 18 share?

All three factorizations contain 3, and multiplying those shared primes gives 3 — exactly the greatest common factor.

Can you get the GCF of 9, 15 and 18 two numbers at a time?

Yes. The GCF of 9 and 15 is 3, and the GCF of 3 and 18 is 3 — the same answer, because the greatest common factor is associative and does not depend on the order of the three numbers.

How does the GCF simplify the ratio 9 : 15 : 18?

Divide every term by the GCF 3: 9 ÷ 3 = 3, 15 ÷ 3 = 5 and 18 ÷ 3 = 6. So 9 : 15 : 18 in lowest terms is 3 : 5 : 6, and no whole number other than 1 divides all three of those.

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