Question

Why can't the product of 2 digit numbers ever be 2 digits

Answer 1

Because the lowest two digit number is 10 and 10 • 10 = 100 so you are already into the three digit numbers and will only go higher.

i hope this help

Answer 2

Because when you multiply for example:
20
x21
And you go through the first thing is you multiply the one out and get 20
Then when you multiply the 2 you add zero to that row, creating a three digit number
20
x 21
---------
20
+ 400
----------
420
Hope this helps