There are 15180 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.
The number of four-digit combinations is 10,000 .Stick a '3' before each of them, and you have all the possible 5-digit combinations that start with 3.There are 10,000 of them. They run from 30,000 to 39,999 .
If you use them only once each, you can make 15 combinations. 1 with all four digits, 4 with 3 digits, 6 with 2 digits, and 4 with 1 digit. There is also a combination containing no digits making 16 = 24 combinations from 4 elements.
16. There are two choices for the first digit (3 and 6). For either choice of first digit there are two choices for the second digit, and so on. 2 x 2 x 2 x 2 = 16.
The number of possible 3 digit combinations you can make out of 1-9 with outrepeated digits is:9C3 = 9!/(3!(9-3)!) = 84
There are 15180 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.
The number of four-digit combinations is 10,000 .Stick a '3' before each of them, and you have all the possible 5-digit combinations that start with 3.There are 10,000 of them. They run from 30,000 to 39,999 .
If you use them only once each, you can make 15 combinations. 1 with all four digits, 4 with 3 digits, 6 with 2 digits, and 4 with 1 digit. There is also a combination containing no digits making 16 = 24 combinations from 4 elements.
16. There are two choices for the first digit (3 and 6). For either choice of first digit there are two choices for the second digit, and so on. 2 x 2 x 2 x 2 = 16.
There are 9C3 = 84 combinations.
There are 1140 5 digit combinations from 1 to 20. 20 combination 3 computes that.
6 of them.
There are 27 possible combinations.
120 combinations using each digit once per combination. There are 625 combinations if you can repeat the digits.
the answer is = first 2-digit number by using 48= 28,82 and in 3 digit is=282,228,822,822