1 3 4 9
There are the digits 1 through 9 for the first digit. Then, we have 0 through 9 for the second digit - excluding the first digit. For the third digit, we have 0 through 9 excluding the two previous digits
That makes:* 8 options for the first digit * 8 options for second digit * 10 options for the third digit * ... etc. Just multiply all the numbers together.
The number of 3-digit numbers with no repeated digits is simply 10x9x8 = 720, if you allow, for example, 012 as a 3-digit number. There are 10 digits, any of which might be the first digit. The second digit can be any digit except the digit that was used for the first digit, leaving 9 possibilities. The third digit then has 8 possibilities, since it can't be the same as the first or second digit. The actual number of possible area codes will be lower, because there are additional restrictions on the number combinations for a valid area code. For example, in North America (USA, Canada, etc.), the first digit of an area code cannot be 0 or 1 and the middle digit cannot be 9.
1000there aren't even 1000 three-digitnumbers...There are the digits 1 through 9 for the first digit. Then, we have 0 through 9 for the second digit - excluding the first digit. For the third digit, we have 0 through 9, excluding the two previous digits for a total of 9*9*8 =81*8 =648 three digit numbers with distinct digits.EDIT- ... to be a little more specific, if your talking about a 3-digit password or unlock code its would be 1000. _-_
60. There are 5 different choices for the first digit, four for the second digit, and three choices for the third digit. According to the fundamental counting principle, you multiply them together to get the total number of possible ways, and 5 x 4 x 3 = 60 Another way to think about it is 5!/3!
1349
4284
Look for the first digit that is different. In this case, the first digit after the decimal point. The number that has the larger digit in this position, is larger. If the first digit is the same, compare the second digit with the second digit, the third digit with the third digit, and so forth, until you find a difference.
182
The first and last, and the second and third.
263
Write them as decimals, and compare. If the first digit of two numbers is equal, compare the second digit; if the second digit is equal, compare the third digit, etc.
The first digit has 4 choices for its digit. The second digit has 6 choices and the third has 3. The solution would simply be 4*6*3=72 three digit numbers.
1155
1
The first digit can have 5 possible numbers, the second digit can have 4, the third 3, the fourth 2. 5
There are the digits 1 through 9 for the first digit. Then, we have 0 through 9 for the second digit - excluding the first digit. For the third digit, we have 0 through 9 excluding the two previous digits