Twodition
We can add a two digit number with another two digit number to get a two digit number.
For example,
22+23=45
or
10+89=99
are such addition operations.
How many such all-two-digit addition operation can we do?
Details:
- We deal only with positive integers.
- 22 + 23 = 45 and 23 + 22 = 45 represents the same operation.
- 22 + 00 = 22 or 22 +07 = 29 and such are not acceptable operations.
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1 solution
Using Mathematica
Length@Select[Union[Sort/@Tuples[Range[10,99],{2}]],IntegerLength@Total@#==2&]returns 1640