Question 1091548: Hi much appreciated math tutors. I am very frustrated by this problem... In a given calling area, telephone numbers have the same three first digits. The four digit number that follows is different for each telephone number. How many numbers are possible? The given answer is 10,000. Please explain in detail the method(s) to solve this. I was thinking the "three first digits" part is irrelevant to the answer and that it just requires finding all the multiples of four digits but I'm not sure. I am "weak" with multiple type problems but am determined to get the concept of them! Thank you for your much appreciated voluntary help!
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! The first three numbers are the same for all, so it doesn't matter.
the last four numbers have 10 choices for the first number, 10 for the second, 10 for the third, and 10 for the fourth. That product is 10000.
Alternatively, between 0000 and 9999 including both are 10,000. The first explanation is a better way to look at problem of this sort. The second is a good way to check it.
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