GCF for 18, 36 and 45

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What's the Greatest Common Factor (GCF) of 18, 36 and 45?

Answer

GCF of 18, 36 and 45 is
9

Common factors: 1, 3, 9

9 divides all three: 18 ÷ 9 = 2, 36 ÷ 9 = 4, 45 ÷ 9 = 5 — and 2, 4 and 5 have no factor but 1 common to all of them, so no larger number divides all three.

18 = 2 × 32

36 = 22 × 32

45 = 32 × 5

Prime183645Lowest power
2222——
332323232
5——5—

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

GCF = 32 = 9

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GCF Table

1st2nd3rdGCF
1830366
1831361
1832362
1833363
1834362
1835361
18363618
1836371
1836382
1836393
1836402
1836411
1836426
1836431
1836442
1836459
1836462
1836471
1836486
1836491
1836502
1836513
1836522
1836531
18365418
1836551
1836562
1836573
1836582
1836591

FAQ

What's the Greatest Common Factor (GCF) of 18, 36 and 45?

GCF of 18, 36 and 45 is 9

What prime factors do 18, 36 and 45 share?

All three factorizations contain 3 × 3, and multiplying those shared primes gives 9 — exactly the greatest common factor.

Can you get the GCF of 18, 36 and 45 two numbers at a time?

Yes. The GCF of 18 and 36 is 18, and the GCF of 18 and 45 is 9 — 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 18 : 36 : 45?

Divide every term by the GCF 9: 18 ÷ 9 = 2, 36 ÷ 9 = 4 and 45 ÷ 9 = 5. So 18 : 36 : 45 in lowest terms is 2 : 4 : 5, and no whole number other than 1 divides all three of those.

See Also