How many 7-digit phone numbers are possible, assuming that the first digit can t be 911
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Hint: Here, first find the total number of ways where the first digit cannot be either 1 or 0. Now, find the total number of ways where the first three-digits can be either 911 or 411. Finally, subtract the number of ways with the second condition from the number of ways with the first condition to find the required number of ways.Complete step-by-step solution: Note: The fundamental principle of multiplication states that, if an operation can be performed in ‘m’ different ways, following which is the second operation can be performed in ‘n’ different ways, then the two operations in succession can be performed in ‘m x n’ ways. How many 7 digit telephone numbers can be formed if the first digit Cannot be 0 or 1?Hence, the answer is 106. Was this answer helpful?
How many combinations of 7 digits are possible?Assuming repetition is allowed, you can have 7-digit numbers from 1,000,000 to 9,999,999 which is a total of 9,000,000 7-digit numbers. These are all the possible 7-digit numbers. In general, there are 9 × 10^(n-1) possible n-digit numbers.
How many seven= 8,000,000. Therefore, according to the condition that the first digit cannot be either 1 or 0, we can have 8,000,000 possible ways of creating a seven-digit area code. Now, according to the other condition which states that the first three-digits cannot have the numbers 911 or 411.
How many possible 9 digit phone numbers are there?Therefore, the total number of possible phone numbers is 7,970,000,000.
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