Question

Find the number of all five digit numbers which have atleast one digit repeated​

Answer 1

Answer:

My thoughts are:

Step-by-step explanation:

I count all the possible numbers of 5 digits: 105=100000. Then, I subtract the numbers that don't have repeated digits, which I calculate this way: 10∗9∗8∗7∗6 =30240. Thus, I have 100000−30240=69760 numbers that have at least one digit repeated more than one time.

Answer 2

Answer:

This is the right answer.

Step-by-step explanation:

We need to multiply the possibilities for each digit.

9 possibilities for the first digit (1-9) and 10 possibilities for the remaining digits (0-9) =9×10×10×10×10=90000

Now, to find numbers that don't repeat any digits. The second digit cannot be equal to the first. The third cannot equal to first and second.The Fourth cannot equal to first , second and third. And the fifth cannot equal to first , second ,third and fourth.

So possibilities will be =9×9×8×7×6=27216

Number repeat at least one digit =90000−27216=62784