Question

Question 18 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.

Class X1 - Maths -Probability Page 405

Answer 1

40% students study Mathematics .
hence, Probability of students study Mathematics = 40/100 = 0.4
P( M) = 0.4

30% students study Biology .
so, Probability of study Biology = 30/100 =0.30
P( B) = 0.3

10% students study both mathematics and biology .hence, Probability of students study both mathematics and biology = 10/100 =0.1
P( M ∩ B) = 0.1

we know,
P( X U Y ) = P( X ) + P( Y ) - P( X ∩ Y )
so, P( M or, B) = P( M U B ) = P( M ) + P( B ) - P( M ∩ B)
= 0.4 + 0.3 - 0.1 = 0.6
hence, Probability of students study Mathematics or biology = 0.6

Answer 2

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