Anne picks a 4-digit number. The first digit is not zero. The 4-digit number is a multiple of 5. How many different 4-digit numbers could she pick?
We know that a digit can be a number between 0 and 9. In this case, the first digit can't be 0, so it has to be a number between 1 and 9. So, we have 9 possible choices for the first digit (1,2,3,4,5,6,7,8,9).The next thing we know is that the number is divisible by 5. Therefore, the final digit of the number must be either 0 or 5. That means that we can only have 2 choices for the fourth digit.Now the second and third digits have no restrictions, so they can be any number between 0 and 9. So for the second digit, we have 10 possible choices (0,1,2,3,4,5,6,7,8,9) and the same applies to the third digit as well. To count the possible number that Anne could pick, we simply multiply the choices we have for each digit and so we get 9210*10=1800
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