Allowing repetitions, there are 9 combinations. Without repeated digits, there is only one combination of 3 digits from 3.
1296 or (6^4)
There are 5,461,512 such combinations.
There are 1140 5 digit combinations from 1 to 20. 20 combination 3 computes that.
I am assuming you mean 3-number combinations rather than 3 digit combinations. Otherwise you have to treat 21 as a 2-digit number and equate it to 1-and-2. There are 21C3 combinations = 21*20*19/(3*2*1) = 7980 combinations.
100
1296 or (6^4)
There are 1140 five digit combinations between numbers 1 and 20.
There are 5,461,512 such combinations.
There are 1140 5 digit combinations from 1 to 20. 20 combination 3 computes that.
There are 9C3 = 10*9*8/(3*2*1) = 120 of them.
There are 840 4-digit combinations without repeating any digit in the combinations.
I am assuming you mean 3-number combinations rather than 3 digit combinations. Otherwise you have to treat 21 as a 2-digit number and equate it to 1-and-2. There are 21C3 combinations = 21*20*19/(3*2*1) = 7980 combinations.
Just 1.
The answer will depend on how many digits there are in each of the 30 numbers. If the 30 numbers are all 6-digit numbers then the answer is NONE! If the 30 numbers are the first 30 counting numbers then there are 126 combinations of five 1-digit numbers, 1764 combinations of three 1-digit numbers and one 2-digit number, and 1710 combinations of one 1-digit number and two 2-digit numbers. That makes a total of 3600 5-digit combinations.
7
100
How many four digit combinations can be made from the number nine? Example, 1+1+2+5=9.