##### Need math help: How many international direct dialing number?

 Mathematics Tutor: None Selected Time limit: 1 Day

How many international direct-dialing numbers are possible if each number consists of a four-digit area code (the first digit of which must be nonzero) and an eight-digit telephone number (the first digit must be nonzero)?
 A. 648,000,000,000 B. 486,000,000,000 C. 810,000,000,000 D. 891,000,000,000 E. 1,215,000,000,000
Nov 15th, 2015

Thank you for the opportunity to help you with your question!

We have 4 + 8 = 12 number of events occurring simultaneously.

Where these 12 events represent the digit values.

1st digit has only 9 possible values.

5th digit has only 9 possible values.

The rest of the 10 digits have 10 possible values.

We multiply their individual possible outcomes and get:

(9^2 )*(10^10) = 810,000,000,000

Answer choice C.) 810,000,000,000

Please let me know if you need any clarification. I'm always happy to answer your questions.
Nov 15th, 2015

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Nov 15th, 2015
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Nov 15th, 2015
May 28th, 2017
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