It should also be noted that rolls below 10 only have 3 digits, making it even more difficult.
Not really. it is exactly the same. 4.12 is 04.12, you see?
Edit:
Taking numbers from 0.00 to 99.99, we have,
number of times 7 appears in tens place = 10^3 = 1000 (70.00 to 79.99 => 7999-7000+1)
ones place = 1000
tenths place = 1000
hundredths place = 1000
Total = 4000. (40%)
Now, you notice that some numbers were counted more than once. for instance, a 77.77 has been counted four times, and a 7.77 or 07.77 has been counted 3 times.
So we reduce that.
3*1 + 2*9*4 + 1*9*9*6 = 561 or 5.61%.
4000-.61 =
3439/10000 or
34.39%.