What two digit number has a GCF of 43?

Answer 1

The gcf of 43 and 129 is 43, so the two digit number must be 43; however

the gcf of 86 and 129 is also 43, so the two digit number must be 86; however

the gcf of 22 and 86 is only 2 and the gcf of 22 and 43 is only 1, no neither 43 nor 86 has a gcf of 43!

Hint:

You cannot have a COMMON factor with only onenumber - common implies at least two numbers.

The greatest COMMON factor is the largest number that divides all the numbers and depends upon all the numbers - it makes no sense to ask for the greatest COMMON factor of a single number.