Find the g.c.d of 15 and 28 .

To get the greatest common divisor of 15 and
28.

Solution :

We  write both
15 and 28 with their prime factor  in their highest
power:

15 =
1*3*5............(1)

28 = 1*2*2*7 = 2^2
*7...........(2)

We examine the factors of 15 and 28 at the
RHS of (1) and (2).

There are no common factors between 15
and 28 except 1.

Therefore 1 is the onl common factor for
15 and 28.

Therefore the GCD or GCF of 15 and 28 is
1.