Maths problem - help needed today!

herewegoagain · Post by **herewegoagain** » Thu Jan 10, 2008 4:34 pm

Can anyone help with this question which is baffling us:

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 form zero. The other three digits can by any number. How many four digit numbers are there?

Thanks!

Wallasey · Post by **Wallasey** » Thu Jan 10, 2008 6:03 pm

Each number has ten possible values, 0-9, and you find the possible number of combinations by multiplying them together. So with 2 numbers it would be 10 x 10 = 100 possibles. Then x another 10 for three numbers = 1000. For the final number, if you can't have zero it's only x 9 this time, so the total would be 9000 possible numbers.

herewegoagain · Post by **herewegoagain** » Thu Jan 10, 2008 8:35 pm

That's really helpful - thanks.