Question

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 or both

Answer 1

P(M) = 0.4
P(B) = 0.3
\[P(M \cap B)=0.1\]
\[P(M \cup B)=P(M)+P(B)-P(M \cap B)\ ..........(1)\]
Now you just need to plug the given values into (1) to find the required probability.

Answer 2

@kropot any difference between these two
1) find the probability that he will be studying Mathematics or Biology
2) find the probability that he will be studying Mathematics or Biology or both

Answer 3

The union of Mathematics with Biology, written as
\[\large M \cup B\]
is defined to be the set consisting of those elements either in M or in B or in both M and B. In mathematics the word 'or' has its inclusive meaning. The inclusive or "M or B"means M or B or both.

Answer 4

P(M∪B)=P(M)+P(B)−P(M∩B)
then why are we subtracting P(M∩B) [ which is the set of student studying m and b ] .

Answer 5

When we add P(M) + P(B) we use the individual probabilities twice relating to outcomes in
\[ M \cap B\]
Therefore to adjust it is necessary to subtract
\[P(M \cap B)\]

Answer 6

@kropot72 thank you

Answer 7

You're welcome :)