Permutation/Combination Question. (1 Viewer)

[syriangabsta]

hmm, Hey , umm I dont know how long it takes for people to realise a new thread has been created, and to reply to it, hopefully it isnt long lol.

Umm, im going over some questions, and ive come across this question thats pissing me off >_<. The question is:

In Australia, home telephones have 8 digits, in Queensland; beginning with a 7. How many different telephone numbers can be accomodated by this system?

Umm, ive realised that, the 7 is always first, so that leaves 7 to rearrange. But then, i noticed that repetition is allowed, and that theres a total of 10 digits to choose from (0-9).

Help will be appreaciated (sp?). Kthx

 

[aalex]

As you said, the first digit must be 7, so there are 7 places left, for each of
them having 10 possibilities (0-9). So the total number of phone numbers is :
1X10^7 (the numbers can be formed in 10^7 different ways)

 

[syriangabsta]

awesome thanks