Solution
For this case we can do the following:
24= 8*3= 2*4*3 = 2*2*2*3
40= 20*2 = 2*10*2= 2*2*2*5
And from the descomposition above we can see that the GCF is :
2*2*2
Since represent the common numbers in both descompositions then the answer is:
GCF= 8
