math
posted by chantelle .
there are 122 houses eacg has number on letter box ,how many times does the digit 2 appear on the letter boxes?

single digit : 2 >1
double digit:
12>1
20, 21, ... 29,> 10
32, 42, 52, 62, 72, 82, 92 > 7
triple digit
102 , 112, 121, 122 >4
see if I missed any, then add them up