Question

How many different phone numbers are possible in the area code 503, if the first number cannot start with a 0 or 1

Answer 1

Answer:

8 X 10^(9)

Step-by-step explanation:

Originally we have 10 digit phone numbers excluding the area code.

For each face value we have these in store: 0,1,2,3,4,5,6,7,8,9 (total 10)

But if we exclude 1 and 0 for the first digit, we are left with 8 digits.

8P1 X .......

In a phone number, digits can repeat so we can choose out of these 10 numbers freely after this.

8P1 X 10P1 X 10P1 X...

Adding the area code while assuming 10P1 is just 10...we get:

1 X 1 X 1 X 8 X 10^(9)

= 8000000000

Very interesting question, thanks for the opportunity!

Answer 2

The number of  different phone numbers in the area code 503, if the first number cannot start with a 0 or 1 should be considered as the $8 \times 10^{(9)}$

Calculation of the number of different phone numbers:

Since

we have 10 digit phone numbers that does not include the area code.

So,

For each face value we have these in store:

0,1,2,3,4,5,6,7,8,9 (total 10)

Now

if we exclude 1 and 0 for the first digit, So it left with 8 digits.

So, it be like

8P1 X .......

Likewise

8P1 X 10P1 X 10P1 X...

Now if add this,

1 X 1 X 1 X 8 X 10^(9)

= 8000000000

hence, The number of  different phone numbers are possible in the area code 503, if the first number cannot start with a 0 or 1 should be considered as the $8 \times 10^{(9)}$

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