GCF (HCF) of 15 and 30

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What is the Greatest Common Divisor of 15 and 30?

Answer

GCF (HCF) of 15 and 30 is
15

Common factors: 1, 3, 5, 15

15 divides 30 (30 ÷ 15 = 2), so the GCF is the smaller number itself.

15 = 3 × 5

30 = 2 × 3 × 5

Prime1530Lowest power
2—2—
3333
5555

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

GCF = 3 × 5 = 15

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GCF Table

Number 1Number 2GCF
15105
15123
15161
15171
15183
15205
15213
15221
15231
15243
15255
15261
15273
15281
15291
153015
15321
15333
15355
15363
15381
15405
15423
15441
154515
15483
15491
15505
15531
15543

FAQ

What is the Greatest Common Divisor of 15 and 30?

GCF (HCF) of 15 and 30 is 15

How to find the GCF of 15 and 30?

You can find the GCF of 15 and 30 by listing all factors of both numbers and picking the greatest common one, or by prime factorization. The GCF of 15 and 30 is 15.

What prime factors do 15 and 30 share?

The prime factorizations of 15 and 30 have 3 × 5 in common, and multiplying those shared primes gives 15 — exactly the greatest common factor.

How does the GCF reduce the fraction 15/30?

Divide the numerator and the denominator by the GCF 15: 15 ÷ 15 = 1 and 30 ÷ 15 = 2. So 15/30 in lowest terms is 1/2.

See Also