ISEE Middle Level Math : How to find the probability of an outcome

Study concepts, example questions & explanations for ISEE Middle Level Math

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Example Questions

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Example Question #71 : Outcomes

If a class has  boys and  girls, what is the probability the teacher will call on a boy?

Possible Answers:

Correct answer:

Explanation:

To find the probability of an event, we will use the following formula:

 

Now, in the event of calling on a boy in the class, we can determine the number of ways the event can happen:

because there are 10 boy students in the class.

 

To find the number of possible outcomes, we get

because there are 22 total students the teacher could potentially call on.

 

Knowing all of this, we can substitute into the formula.  We get

Reduce:

 

Therefore, the probability of calling on a boy is .

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