Question 1191918
<br>
The question is not clear.<br>
Are you looking for the number of permutations of the 3 of the n objects, or the number of permutations of all n objects?<br>
My reading of the problem suggests that the question being asked is the number of permutations of the 3 objects.<br>
In that case, the solution is easy.<br>
{{{C(n,3) = ((n)(n-1)(n-2))/(3*2*1) = ((n)(n-1)(n-2))/6}}}<br>
{{{P(n,3) = (n)(n-1)(n-2)}}}<br>
Therefore, given C(n,3)=20, we can immediately deduce that P(n,3) is 6*20 = 120<br>
ANSWER (the way I read the problem): 120<br>