A final examination requires that a student answer any 4 out of 6 questions. In how many ways can this be done?
-
A.
15 -
B.
20 -
C.
30 -
D.
45
Correct Answer: Option A
Explanation
The question will be answered in
(^5C_4 = frac{6!}{(6-4)!4!}\=frac{6!}{2!4!}\=frac{6times5times4!}{2times1times4!}\=15hspace{1mm}ways)