



 
Hi Miranda, Think about trying to write down all the account numbers in the following way. Write down all the possible first digits. There are 9 since the first digit can't be 0. You can now extend each of these one digit numbers to a two digit number using any of the ten digits as the second digit. Thus there are 9 10 = 90 possible two digit numbers. You can now extend each of these two digit numbers to a three digit number using any of the ten digits as the third digit. Thus there are 9 10 10 = 900 possible three digit numbers. Can you complete it now?  


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