There is no limitation given to the number of digits in the number, thus:
For 3 digit numbers: to be less than 500 the first digit can be only one of {1, 2, 3, 4} leading to 4 × 5 × 4 = 80 numbers
For 2 digit numbers: they are all less than 500, and there are 6 × 5 = 30 numbers
For 1 digit numbers: they are all less than 500, and there are 6 numbers
Thus there are in total 80 + 30 + 6 = 116 numbers that can be made form the digits {1, 2, 3, 4, 5 ,6} without repetitions that are less than 500.
# 230 # 203 # 320 # 302
There are 60480 numbers.
1 set
There are 4^6 = 4096 such numbers.
If the digits are all different then 18. Otherwise, 192.
504
pizza
There are 5 numbers of 1 digit, 25 numbers of 2 digits, and 75 numbers of 3 digits. This makes 105 numbers in all.
27 three digit numbers from the digits 3, 5, 7 including repetitions.
2,401
10,000
Assuming all 45 digits are different (which they will not be if they are ordinary integers), then 456, if repetitions are allowed. That is 8303765625. If repetitions are not allowed then the number falls to 45*44*43*42*41*40 = 5864443200
5^4
15 of them.
I take it that you want to make three digits numbers with 8,7,3, and 6 without repetition. The first digit cane be selected from among 4 digits, the second from 3 digits, the third digit from 2, hence the number of three digit numbers that can be formed without repetition is 4 x 3 x 2 = 24
99999
5040 different 4 digit numbers can be formed with the digits 123456789. This is assuming that no digits are repeated with each combination.