How many strings of three decimal digits (0, 1, 2, …, 9)
a) do not contain the same digit three times?
b) begin with an odd digit?

Question

How many strings of three decimal digits (0, 1, 2, …, 9)
   a) do not contain the same digit three times?
   b)  begin with an odd digit?

anonymous · Answer

Consider that there are

10 x 10 x 10 total strings of 3-digit numbers (if you allow leading 0's)

There are only 10 where all digits are the same (all 0's through all 9's)

So, you have:  10 x 10 x 10  -  10 strings where you don't have 3 identical digits.

As for your second question, there are:

5 x 10 x 10 that start with an odd digit which happens to be the same as the number that start with an even digit.

anonymous · Answer

All good now, @sweetshiva9963  ?

sweetshiva9963 · Answer

Yea

anonymous · Answer

Ok!  Glad I was able to help you! @sweetshiva9963

anonymous · Answer

Good luck to you in all of your studies and thx for the recognition! @sweetshiva9963

sweetshiva9963 · Answer

your welcome. Thanks for the help

anonymous · Answer

anytime!