How many times does the digit 1 occur in ten place in the numbers from 1 to 1000?
there are no 3 digit tis two digit! :) * * * * * 90 of them.
90 of them.
There are 900,000,000 of them.
There are 90 of them.
There are 5 of them.
There are no pairs of 2-digit numbers with a difference of 90 if both numbers are positive or both negative. However, with one positive and one negative, there are 71 pairs.
There are infinitely many such numbers. For example, 123,456,063