Telephone number and digits
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Telephone number and digits
Can anyone help with the following?
The last part of a telephone number has four digits eg
7814 1487 2103 2772
The last part of the telephone number can start with any digit apart from zero. The other three digits can be any number. How many four digit numbers are there?
The last part of a telephone number has four digits eg
7814 1487 2103 2772
The last part of the telephone number can start with any digit apart from zero. The other three digits can be any number. How many four digit numbers are there?
Re: Telephone number and digits
X X X X
How many digits can go in place 1? Place 2? .... so how many options altogether?
How many digits can go in place 1? Place 2? .... so how many options altogether?
Re: Telephone number and digits
Thanks! DD had put 9000 so I wanted to try and work out if she was correct 
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Surferfish
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Re: Telephone number and digits
Yes I think your DD is correct.
The way I would think of it is, if there were no restrictions on any of the digits the number of possibilities would obviously be 10,000. (0000 - 9999).
But you are not allowed 0000 - 0999 so you have to subtract these 1000 numbers leaving 9000.
The way I would think of it is, if there were no restrictions on any of the digits the number of possibilities would obviously be 10,000. (0000 - 9999).
But you are not allowed 0000 - 0999 so you have to subtract these 1000 numbers leaving 9000.