Phone numbers
How many 9-digit telephone numbers can be compiled from the digits 0,1,2,..,8,9 that no digit is repeated?
Correct answer:
Showing 1 comment:
Mathyu
Solution is not correct. 0-9 is 10 digits, so n = 10 * 9 * 8 * 7 * 6 * 5 * 4 = 604800. Or, 10!/3! = 604800. If there was a restriction on the first digit, such that the first digit could not be 0 or 1, or any other number, then it would be 9. However, there is no restriction (that is given) to make this valid, so for the first digit, there are initially 10 digits to choose from. After one is taken, then it goes to 9 and etc.
6 years ago 6 Likes
Tips for related online calculators
You need to know the following knowledge to solve this word math problem:
Related math problems and questions:
- Repeated 79734
How many numbers a) less than 500, b) greater than 500 can be formed from the digit 0,1,5,8,9 so that no digit is repeated? - Numbers
How many different 4 digit natural numbers in which no digit is repeated can be composed of digits 0,1,2,3? - Dd 2-digit numbers
Find all odd 2-digit natural numbers compiled from digits 1; 3; 4; 6; and 8 if the digits are not repeated. - How many 4
How many four-digit numbers that are divisible by ten can be created from the numbers 3, 5, 7, 8, 9, and 0 such no digits repeats?
- Double-digit 33471
How many double-digit numbers greater than 60 can we make from digits 0,5,6,7,8,9? The numerals must not be repeated. - Three-digit number
How many three-digit natural numbers can we form from the digits 0, 1, and 2 if the numerals can be repeated in these numbers? - Ascending 32663
How many natural numbers can you make from the digits in 4052? No digit may be repeated in the number entry. Sort the numbers in ascending order of size.
