GCF (HCF) of 15 and 40

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Greatest Common Factor of
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What is the Greatest Common Divisor of 15 and 40?

Answer

GCF (HCF) of 15 and 40 is
5

Common factors: 1, 5

5 divides both: 15 ÷ 5 = 3, 40 ÷ 5 = 8 — and 3 and 8 share no factor but 1, so no larger number divides both.

15 = 3 × 5

40 = 23 × 5

Prime1540Lowest power
2—23—
33——
5555

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

GCF = 5

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GCF Table

Number 1Number 2GCF
15213
15221
15231
15243
15255
15261
15273
15281
15291
153015
15321
15333
15355
15363
15381
15405
15423
15441
154515
15483
15491
15505
15531
15543
15555
15561
156015
15641
157515
15771

FAQ

What is the Greatest Common Divisor of 15 and 40?

GCF (HCF) of 15 and 40 is 5

How to find the GCF of 15 and 40?

You can find the GCF of 15 and 40 by listing all factors of both numbers and picking the greatest common one, or by prime factorization. The GCF of 15 and 40 is 5.

What prime factors do 15 and 40 share?

The prime factorizations of 15 and 40 have 5 in common, and multiplying those shared primes gives 5 — exactly the greatest common factor.

How does the GCF reduce the fraction 15/40?

Divide the numerator and the denominator by the GCF 5: 15 ÷ 5 = 3 and 40 ÷ 5 = 8. So 15/40 in lowest terms is 3/8.

See Also