Highest common factor of 72 and 28

4

NOTE: ONLY REFER FIRST METHOD IF YOU ARE FROM CLASSES BELOW 5TH GRADE AND IF YOU KNOW THEM BOTH ITS OK.

First we list factors of both 28 & 78

28: 1,2,4,7,14,28

78: 1,2,3,4,6,8,9,12,18,24,36,72

Now the common factors are, 1,2,4

And we know that 1<2<4

And thus 4 is the highest common factor

Another way is prime factorisation:

In this method, we need to find the prime factors of both the given numbers and find out the common factors and mutiply them.

So, 28: 2*2*7 and 72: 2*2*2*3*3

In now we see that, 2*2 is common in  both common prime factors of both 28&72, Thus we get  2*2, And after solving it we get the highest common factor as 4