What is the greatest common factor of 51 and 85?

Answer 1

To find the greatest common factor of two numbers, they first need to be split into their prime factors. For 85 and 51 this is done as follows:

51 = 17x3

85 = 17x5

The next step is to identify any common factors. In this case, both numbers have 17 as a prime factor. This is the only common factor, and thus the greatest common factor of 85 and 51 is 17.

Answer 2

The greatest number which divides both 51 and 85 is 17. So, greatest common factor is 17.

Alternate method:

P.F. of 51 = 3x17

P.F. of 85 = 5x17

Clearly, from the P.F. of both numbers 17 is the greatest common factor.
The GCF is 17.
51 and 85's highest common factor is 17.

Answer 3

The GCF= 17