#1**0 **

*How many two-digit numbers have non-zero digits whose sum is prime?*

I don't know a way to do this except by brute force.

What "brute force" means, in mathematics, is that you just try everything.

Like so:

12, 14, 16

21, 23, 25, 29

32, 34, 38

41, 43, 47, 49

52, 56, 58

61, 65, 67

74, 76

83, 85, 89

92, 94, 98

I stacked them like that to see if I could detect a pattern. I couldn't.

I made this list quickly in my head so I might've missed one/some.

If I didn't overlook one/some, the total is **28**. Check my work.

_{.}

Guest Aug 1, 2021