There are 8*7/(2*1) = 28 combinations.
There are 9C2 = 9*8/(2*1) = 36 2-digit combinations.
There are 11C2 = 11*10/(2*1) = 55 combinations.
Assuming the digits cannot be repeated, there are 7 combinations with 1 digit, 21 combinations with 2 digits, 35 combinations with 3 digits, 35 combinations with 4 digits, 21 combinations with 5 digits, 7 combinations with 6 digits and 1 combinations with 7 digits. That makes a total of 2^7 - 1 = 127: too many for me to list. If digits can be repeated, there are infinitely many 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.
There are 8*7/(2*1) = 28 combinations.
There are 9C2 = 9*8/(2*1) = 36 2-digit combinations.
There are 11C2 = 11*10/(2*1) = 55 combinations.
Assuming the digits cannot be repeated, there are 7 combinations with 1 digit, 21 combinations with 2 digits, 35 combinations with 3 digits, 35 combinations with 4 digits, 21 combinations with 5 digits, 7 combinations with 6 digits and 1 combinations with 7 digits. That makes a total of 2^7 - 1 = 127: too many for me to list. If digits can be repeated, there are infinitely many combinations.
7C3 = 7*6*5/(3*2*1) = 35 combinations.7C3 = 7*6*5/(3*2*1) = 35 combinations.7C3 = 7*6*5/(3*2*1) = 35 combinations.7C3 = 7*6*5/(3*2*1) = 35 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.
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You can make 5 combinations of 1 number, 10 combinations of 2 numbers, 10 combinations of 3 numbers, 5 combinations of 4 numbers, and 1 combinations of 5 number. 31 in all.
There are 5C3 = 5*4/(2*1) = 10 combinations
There are 233 - 1 = 8,589,934,591 combinations, not including the null combination.
4*3*2*1 = 24 different combinations.
There are 8C6 = 8*7/(2*1) = 28 combinations.