A student has to take 4 of the following 7 classes before they are allowed to graduate: chemistry, biology, physics, economics, computer science, theatre, and rhetoric. How many ways can a student choose 4 classes? When looking at random selection, what is the probability that a student's choice will not have included physics?

Question

kropot72 · Answer

The number of ways of choosing 4 classes from the 7 that are available is 7C4.
$$7C4=\frac{7!}{4!3!}=you\ can\ calculate$$
The probability that a student's choice will not have included physics is found by dividing the number of ways of choosing 4 classes from 6 (thereby excluding physics from the selection) by the number of ways of choosing 4 classes from the 7 that are available.
Therefore the required probability is
$$\frac{7C4}{6C4}=you\ can\ calculate$$

anonymous · Answer

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