Which two of the following numbers are co-prime? 28, 35, 42, 45, 60, 72
A
28 and 35
B
35 and 72
C
42 and 60
D
45 and 72
Number Prime Factors
28 2^2, 7
35 5, 7
42 2, 3, 7
45 3^2, 5
60 2^2, 3, 5
72 2^3, 3^2
The only two with no factors in common are 35 and 72.
+483 
