There are 4845 combinations of 4 numbers from the set 1 - 20
nCr = n!/r!(n-r)!
⇒ 20C4 = 20!/4!(20-4)!
= 20 x 19 x 18 x 17/4 x 3 x 2 x 1
= 4845
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Only one, since the order of the numbers does not matter in a combination.
How many numbers are there are in each combination ?If one, then 4 combinations.If two, then 6 combinations.If three, then 4 combinations.If four, then only 1 combination.
120 WRONG! That is the number of PERMUTATIONS. In the case of combinations, the order of the numbers does not matter, so there is only 1 5-number combination from 5 numbers.
262
There are 360 of them.