What ways to make 21?

Answer 1

There are infinitely many possible additions:

10+11, 9+12, 8+13, 7+14, ....

and then

10.5+10.5, 10.4+10.6, 10.3+10.7, 10.2+10.8, ....

and then 2 digit

10.49 + 10.51, 10.48+10.52, ...

and 3 digit, 4 digit, ... infinitely many digits.

Next, you can look at multiplication:

1x21, 2x10.5, 3x7, and so on

and then 0.1x210, 0.2*105, 0.3*70 and so on

and then 2 digit decimals fractions, and then 3 digit, 4 digit, and so on, and on.

And I have not even started on 3 or more numbers, or powers and other mathematical functions.

Answer 2

There are several ways to make 21, such as adding 10 and 11, adding 15 and 6, or multiplying 3 and 7. Another way is subtracting 1 from 22.