On an examination, a student is to select any 4 questions out of 7 to answer.
a. How many different sets of 4 questions can be selected?
b. How many sets of 4 questions will include question 1?
c. If a student answers 4 questions out of 7 on a test, what is the probability that he selected question1?

Question

On an examination, a student is to select any 4 questions out of 7 to answer.
a. How many different sets of 4 questions can be selected?
b. How many sets of 4 questions will include question 1?
c. If a student answers 4 questions out of 7 on a test, what is the probability that he selected question1?

inkyvoyd · Answer

a. 7C4
b. 4/7 times total
c. wow.

anonymous · Answer

$\dbinom{7}{4}=35$

.sam. · Answer

@satellite73 you're good at statistics :)

anonymous · Answer

$$\dbinom{6}{4}=15$$ for the second one

anonymous · Answer

i know absolutely no statistics sorry

inkyvoyd · Answer

EMPIRICAL RULE FTW FTW

inkyvoyd · Answer

EVEN CALCULUS HATES THE ERF()

anonymous · Answer

what's c? I know it's not 0...

anonymous · Answer

if question one is selected, then so are three out of the other 6 so answer i s
$$\frac{\dbinom{6}{3}}{\dbinom{7}{4}}$$