What 3 numbers add to 15?

Answer 1

18

Answer 2

There are infinitely many triplets.5 + 5 + 5

5 + 4.9 + 5.1

5 + 4.8 + 5.2 and so on.

And then, consider triplets where the second and third numbers have two digits after the decimal point:

5 + 4.99 + 5.01

5 + 4.98 + 5.02 and so on.

Next move to triplets where the second and third numbers have three digits, four digits, ... infinitely many digits after the decimal point.

All along, the first number has been 5. Replace it with 5.1 and go through the whole process again. And so on.