Eleven.
40, 80, 120, 160, 200 +40 . . .
It is 1
Not as a whole number because 1/40 = 0.025
The gcf is 8
2..
40 and 63 have no common prime factors.
There are an infinite number of them. If you're only interested in positive, whole numbers, then there are 8 of them: 1, 2, 4, 5, 8, 10, 20, and 40.
Only the number 1.
It is 280
easy, 40
Their HCF is 8
One.