You need two number to get a common factor. A single number doesn't have any.
The GCF of 27, 36 and 54 is 9. The GCF of 2736 and 54 is 18.
It is: 2736
2736
The LCM is 2736.
It is: 2736/5 = 547.2
No, 15 is not a factor of 72.
15
1
It is 16
3
It is: 25
It is: 2