# How many 7 digit phone numbers are possible if the first digit cannot be 0

Telephone Number Permutations Using the fundamental principle of counting or permutations how many 7 digit telephone numbers are possible if the first digit cannot be 0 and A. only odd digits may be used. Apr 27, 2020 · According to the North American Numbering Plan Administration (NANPA) standards, U.S. phone numbers contain a 3-digit area code, followed by a 3-digit exchange code and end in a 4­digit subscriber number. The first digit of both the area code and exchange code cannot be 0 or 1. Apr 16, 2019 · It depends if the number can start with zero and if digits can repeat. If digits can repeat and it can start with zero than there are 10 options for every digit so the answer is 10**7, or 10000000. The first digit is $0$. The remaining digits can be any number ranging from $0$ to $9$. How many possible telephone numbers are there? My try: I first said that since the first digit is $0$, we only need to look at the remaining $9$ digits and see how many different ways they can be arranged. If the $9$ remaining numbers can be from $0$ to $9$. Telephone Number Permutations Using the fundamental principle of counting or permutations how many 7 digit telephone numbers are possible if the first digit cannot be 0 and A. only odd digits may be used. How many 7-digit phone numbers can be formed if the first digit cannot be 0 or 1, and if no digit can be repeated? 483,840 How many different ways can be the letters of each of each word be arranged: MONDAY The third digit has 8 possibilities: it can be any number except the same as the first two, but it CAN be 5. The fourth digit has 7 possibilities, it can be any number except the same as the first three. ANd so on; each successive digit has one fewer possibility than the digit before. We end up with. 9 * 9 * 8 * 7 * 6 * 5 * 4, which is 544,320. The decimal number system has 10 digits, 0-9. Two digits may represent 100 values, 00-99. This is 10*10.= 100. If the first digit may not be 0, this is 9*10. If the first and fourth digits of a ten digit telephone number may not be 0 or 1, then the number of unique phone numbers is: 8*10*10*8*10*10*10*10*10*10 Jun 25, 2016 · So the total number of ways the word MISSISSIPPI can be permuted $= \mathbf{\dfrac{10!}{4!4!2!}}$. How many 7-digit phone numbers are possible, assuming that the first digit cannot be a 0 or a 1? There are $\mathbf{10}$ (digits 0-9) possibilities for digits from 2 to 7. The 1st digit has $\mathbf{8}$ possibilities (digits 2-9). The third digit has 8 possibilities: it can be any number except the same as the first two, but it CAN be 5. The fourth digit has 7 possibilities, it can be any number except the same as the first three. ANd so on; each successive digit has one fewer possibility than the digit before. We end up with. 9 * 9 * 8 * 7 * 6 * 5 * 4, which is 544,320. How many different seven-digit telephone numbers can be formed if the first digit cannot be zero? Step-by-step solution: 100 %( 42 ratings) How many 7-digit telephone numbers are possible if the first digit cannot be zero and no repetitions are allowed? The Probability of Dependent Events: In mathematics, dependent events are events ... Answer to How many different 7 digit phone numbers are possible if the first digit cannot be 0 or 1 and the second digit cannot b... Each digit can be any number 0 - 9. The only exception is that all four digits cannot be the same (e.g. the combination can’t be 1111, 2222, etc.) How many combinations are possible on a standard combination lock? How many 7-digit telephone numbers are possible if the first digit cannot be. eight and (a) only even digits may be used? (b) the number must be a multiple of 10 (that is, it must end in 0)? (c) the number must be a multiple of 1,000? (d) the first 2 digits are 92? (e) no repetitions are allowed? The first digit can be formed in 8 ways (excluding 0 and 1). The rest of the 6 digits each can be filled in 10 ways. The total number of digits, therefore is 8 x 10^6. The total number of digits are (from 0-9) {eq}10 {/eq}. We have to find the number of five-digit odd numbers. Since the first digit cannot be zero,... May 29, 2008 · Sequential Counting Principle (SCP): Telephone numbers within the same area code consist of seven digits. For local calls, the first digit cannot be a 0 or a 1. How many local telephone numbers are po … read more The first digit is $0$. The remaining digits can be any number ranging from $0$ to $9$. How many possible telephone numbers are there? My try: I first said that since the first digit is $0$, we only need to look at the remaining $9$ digits and see how many different ways they can be arranged. If the $9$ remaining numbers can be from $0$ to $9$. How many different seven-digit telephone numbers can be formed if the first digit cannot be zero? Step-by-step solution: 100 %( 42 ratings) how many 7-digit telephone numbers are possible if the first digit cannot be 0 and only odd digits may be used? no. of odd digits = 5. total possible nos. = 5^7 Think of it this way - There are 8 different possibilities for the first number: the numbers 2–9 For the second number there are ten possibilities: 0–9 The trick here is that there are 10 possibilities for each one of the first number possibilitie... Jun 25, 2016 · So the total number of ways the word MISSISSIPPI can be permuted $= \mathbf{\dfrac{10!}{4!4!2!}}$. How many 7-digit phone numbers are possible, assuming that the first digit cannot be a 0 or a 1? There are $\mathbf{10}$ (digits 0-9) possibilities for digits from 2 to 7. The 1st digit has $\mathbf{8}$ possibilities (digits 2-9). The first digit can be formed in 8 ways (excluding 0 and 1). The rest of the 6 digits each can be filled in 10 ways. The total number of digits, therefore is 8 x 10^6. Jan 28, 2016 · Next, there are 9 ways to pick the second digit [0 plus the remaining 8 from the first digit] The 3rd digit is chosen from the remaining 8 numbers. The 4th digit is chosen from the remaining 7 numbers. The 5th digit is chosen from the remaining 6 numbers. The 6th digit is chosen from the remaining 5 numbers. The decimal number system has 10 digits, 0-9. Two digits may represent 100 values, 00-99. This is 10*10.= 100. If the first digit may not be 0, this is 9*10. If the first and fourth digits of a ten digit telephone number may not be 0 or 1, then the number of unique phone numbers is: 8*10*10*8*10*10*10*10*10*10 The total number of digits are (from 0-9) {eq}10 {/eq}. We have to find the number of five-digit odd numbers. Since the first digit cannot be zero,... May 29, 2008 · Sequential Counting Principle (SCP): Telephone numbers within the same area code consist of seven digits. For local calls, the first digit cannot be a 0 or a 1. How many local telephone numbers are po … read more Assuming that the first digit of the 4 digit number cannot be 0, then there are 9 possible digits for the first of the four. Also assuming that each digit does not need to be unique, then the next ... Mar 29, 2020 · How many 10-digit telephone numbers (area code + number) are possible if the first digit cannot be zero, the first three digets cannot be 800 or 900, and the number myst end in 0000? May 29, 2008 · Sequential Counting Principle (SCP): Telephone numbers within the same area code consist of seven digits. For local calls, the first digit cannot be a 0 or a 1. How many local telephone numbers are po … read more Apr 16, 2019 · It depends if the number can start with zero and if digits can repeat. If digits can repeat and it can start with zero than there are 10 options for every digit so the answer is 10**7, or 10000000. Greek telephone numbers are ten digits long, and usually written AAB BBBBBBB or AAAB BBBBBB where AAB or AAAB is the 2- or 3-digit national area code plus the first digit of the subscriber number, and BBBBBBB or BBBBBB are the remaining digits of the subscriber number. The entire number must always be dialed, even if calling within the same ... Apr 02, 2007 · (a) The first digit can be selected in 7 ways (7, 9 and 0 are not allowed). Restriction on "0" is implicit, otherwise you will form a 6 digit number. The remaining digits can be selected in 10 ways each. Therefore, answer is 7x10^6 (b) Answer = 50 x 7 x 10^6 Apr 02, 2007 · (a) The first digit can be selected in 7 ways (7, 9 and 0 are not allowed). Restriction on "0" is implicit, otherwise you will form a 6 digit number. The remaining digits can be selected in 10 ways each. Therefore, answer is 7x10^6 (b) Answer = 50 x 7 x 10^6 If, however, you can not use the same number twice in completing the 4 digit number, and the first digit cannot be 0, then the result is 9x9x8x7 = 4536 possible 4 digit numbers.