9.8.2. Complementary Events and the Difference between Two Events

A classroom has 49 students; 23 of them read Al-Akhbar newspaper, 21 read Al-Ahram newspaper and 5 read both. If a student is selected at random, calculate the probability that the student reads Al-Ahram newspaper.

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• B
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• D

Example

A classroom has 49 students; 23 of them read Al-Akhbar newspaper, 21 read Al-Ahram newspaper and 5 read both. If a student is selected at random, calculate the probability that the student reads Al-Ahram newspaper.

Solution

The probability of event occurring is equal to the number of favorable outcomes divided by the total number of possible outcomes in the sample space, . In this case, event is selecting a student who reads Al-Ahram newspaper. Find the probability of event as follows, keeping in mind that the students who read Al-Ahram newspaper include the students who read both newspapers.

Thus, the probability of selecting a student who reads Al-Ahram newspaper is .

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