How Many Phone Numbers Can There Be?

How many combinations of 5 numbers are there?

120Hence there are 2 choices for the fourth digit and only 1 choice for the fifth digit.

Thus you have made 5 × 4 × 3 × 2 1 = 120 choices and there are 120 possible 5 digit numbers made from 1, 2, 3, 4 and 5 if you don’t allow any digit to be repeated.

Now consider the possibilities with 13 as the first two digits..

What are the possible combinations of 6 numbers?

If you are just using the digits from 1 to 6, the answer would be 6*5*4*3*2*1 = 720, because you have 6 choices for the units digit, and then 5 choices left for the tens, and then 4 choices left for the hundreds and so on.

What is the maximum number of digits in a phone number?

15 digitsA telephone number can have a maximum of 15 digits. The first part of the telephone number is the country code (one to three digits)

WHEN DID phone numbers go from 5 to 7 digits?

1947 to 1951 Several cities were upgraded in this period to seven-digit (two-letter-five-number) phone numbers. As there are no letters on the 0 or 1 position, it fit with the assumption that no central office code would have a zero or one as the middle digit.

What is the smallest whole number?

Which is the smallest whole number? Solution. Zero (0) is the smallest whole number.

How do you calculate the number of possible combinations?

Review the formula for combinations. The formula for combinations is generally n! / (r! (n — r)!), where n is the total number of possibilities to start and r is the number of selections made. In our example, we have 52 cards; therefore, n = 52.

Are all phone numbers the same length?

The length of the telephone number varies depending on the country you are calling. In many European countries, phone numbers are variable in length, ranging from just five or six digits in small towns to ten or more in large cities. In the United States, phone numbers are fixed-length, with a total of 10 digits.

Is 7 a magic number?

brain_seven_dice_topNteaser. … This limit, which psychologists dubbed the “magical number seven” when they discovered it in the 1950s, is the typical capacity of what’s called the brain’s working memory.

What is a 7 digit number called?

The smallest 7-digit number is 1 followed by 6 zeros. This number is called one million. The largest 7-digit number is 9 followed by another 6 nines. This number is called nine million nine hundred ninety-nine thousand nine hundred ninety-nine.

What is the first 3 digits of a phone number called?

Unsourced material may be challenged and removed. A telephone prefix is the first set of digits after the country, and area codes of a telephone number; in the North American Numbering Plan countries (country code +# ), it is the first three digits of a seven-digit phone number, 3-3-4 scheme.

What is the largest whole number?

There is no ‘largest’ whole number. Except 0, every whole number has an immediate predecessor or a number that comes before. A decimal number or a fraction lies between two whole numbers, but are not whole numbers.

How many combinations are there in a 10 digit number?

9,999,999,999If you have 10 digits then the maximum number possible is: 9,999,999,999. Since the sequence starts at 0 we need to add 1. So 10,000,000,000 (10 billion). That is how many numbers can be represented in 10 digits, it is not the number of phone numbers possible.

Why are there 7 numbers in a phone number?

The original phone numbers were 5 character long in some regions. Later on the mnemonic system produced longer telephone numbers like PEnnsylvania 4-4500, growing to 7 digits. In addition, there was a growing menagerie of mnemonic words that were making the system nearly impossible to use.

How many permutations are there in 10 numbers?

10,000,000,000If repetition is allowed, then the number of permutations of 10 digits is 10,000,000,000.

How many combinations of 6 numbers are there in 59?

45,057,474The number of combinations possible with 6 numbers between 1 and 59 is 45,057,474.