Question

Most phone numbers have seven digits after the area code, where each digit can be 0-9. How many different phone numbers can there be in one area code

Answer 1

9 × 10⁶ = 9,000,000

Step-by-step explanation:

Data provided in the question:

The phone number is of 7 digits

also,

we have choices from 0-9 i.e 10 number of choices

So,

we have 10 choices out of 10 for each of the 7 blanks

Therefore,

The total number of different phone numbers can there be in one area code that can be formed

= 10 × 10 × 10 × 10 × 10 × 10 × 10

= 10^7

= 10,000,000

Answer 2

9 × 10⁶ = 9,000,000

Explanation:

Data provided in the question:

The phone number is of 7 digits

i.e

we have 7 blanks to fill

also,

we have choices from 0-9 i.e 10 number of choices

Now,

the first digit of the number cannot be zero

Thus,

we have only 9 choices out of 10 for the first digit

And, for the rest of the 6 blanks we have 10 choices for each

Therefore,

The total number of different phone numbers can there be in one area code that can be formed

= 9 × 10 × 10 × 10 × 10 × 10 × 10

= 9 × 10⁶

= 9,000,000