Euclidean Algorithm

According to the Euclid's algorithm, we start with 2 numbers, a and b. 

We do $a ÷ b = c$ with remainder R where a is the larger of the two. 

Then, we replace a with b and b with R, and do the same thing. 

We repeat this prcoess until R is 0. 

So, now we do the same with 972 and 1220. 

$1220 ÷ 972 = 1; R= 248$

$972 ÷ 248 = 3 ; R =228$

$248 ÷ 228 = 1 ;R= 20$

$228 ÷ 20 = 11 ;R= 8$

$20 ÷ 8 = 2 ;R =4$

$8 ÷ 4 = 2 ;R =0$

When the remainder is 0, the GCF is the divisor. Thus, 4 is the GCF. 

So our answer is 4. 

Thanks! :)

~NTS