|
Now, we can start to do some cool counting!
Let's figure out how many phone
numbers there are in each area code:
Phone
numbers have 7
digits...
What
we'll do is pick the first digit, then
the second digit, then the
third, and so on.
(Just like dialing!) This will allow us to use the
counting principle!
OK, so the possible digits are:
Ten possibilities!
Pick the first digit:
Typically, I'd say
that there would be 10
choices here... But, we can't start a phone number with a
0
or a 1...
So, there are 8
possibilities here:
Now, we pick the
second digit -- no restrictions here...
10
possibilities
and
10
for each digit after that:
Since we picked slot
1,
then slot 2,
and so on, we get to use the counting principle:
So, there are
8,000,000
possible phone numbers.
Continued on the
next
page
|
The printing
and distribution and/or downloading of these lessons is strictly
prohibited. |
|
