if only digits 0,1,2,3,4,5,6, and 7 may be used find number of possibilites four digit numbers

n!/r!(n-r)!

8!/4!(8-4)!
= 70

Ok, Andrew

in my last answer to the same question I somehow missed the 7 and saw only 6 numbers.
(Have to concentrate more on reading the question more carefully)

In each case we can assume that no whole number starts with a zero, and no repeating digits for all 3 cases.
We have 8 digits, but can only use 7 in the first position ...

number of 4 digits numbers = 7x7x6x5 = 1470
number of 3 digit odd numbers, (must end in an odd) = 6x6x4 = 144

number of 3 digit numbers = 7x7x6 = 294

Life in Base 14


The only digits allowable in these problems are {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, @, ^, *, #} where @, ^, *, and # are 10, 11, 12, and 13 respectively. All numbers are in base 14. Answers need to be in base 14. Solve the following in Base 14 and show your work in base 14. (each is worth ½ a bonus point if correct with work)
1. Savannah had some pencils. She gave 25 to Jerry. Now she has 7 pencils left. How many pencils did Tom have to start with?

2. Savannah had 5^ pencils. Jerry gave her 7# more. How many pencils does Tom have altogether?

3. Tom has 3@ pencils. Jerry has 4* pencils. How many more pencils does Jerry have than Tom?

4. A large rectangular warehouse is 82 feet long on one side and 1@ feet wide on another side. The floor is to be tiled with square ceramic tiles which are each 1 foot on a side. How many tiles will it take to complete the floor?

5. The drum corps consists of 14 rows of drummers with 34 drummers in each row. How many drummers are there in the corps?

To find the number of possibilities for a four-digit number using only the digits 0 to 7, we need to consider the number of choices for each digit position.

For the first digit position, we have 8 choices (0, 1, 2, 3, 4, 5, 6, and 7).

For the second digit position, again we have 8 choices (0, 1, 2, 3, 4, 5, 6, and 7).

The same goes for the third digit position, where we still have 8 choices.

Finally, for the fourth digit position, we also have 8 choices.

To find the total number of possibilities for the four-digit number, we need to multiply the number of choices for each digit position:

8 choices for the first digit position ×
8 choices for the second digit position ×
8 choices for the third digit position ×
8 choices for the fourth digit position

Mathematically, this can be expressed as 8 × 8 × 8 × 8, which equals 4096.

Therefore, there are 4096 possible four-digit numbers that can be formed using only the digits 0, 1, 2, 3, 4, 5, 6, and 7.