Q40 of 43 Page 15

In Class XI of a school 40% of the students study Mathematics and 30% study Biology. 10% of the class study both Mathematics and Biology. If a student is selected at random from the class, find the probability that he will be studying Mathematics or Biology.


Let E, F denote the events that a student studies Mathematics and Biology respectively.

P(E) = 0.40

P(F) = 0.30

P(E ∩ F) = 0.10

P(Mathematics or Biology )

= P(E ∪ F)

= P(E) + P(F) – P(E ∩ F)

= 0.40 + 0.30 – 0.10

= 0.70 – 0.10 = 0.60

P(E ∪ F) = 0.60.

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42
The probability that a student will pass the final examination in both English and Hindi is 0.5 and the probability of passing neither is 0.1. If the probability of passing the English examination is 0.75, what is the probability of passing the Hindi examination?