Two thirds of the students in a class are boys and the rest girls. It is known that eh probability of a girl getting a first class is 0.25 and that of a boy getting a first class is 0.28. find the probability that a student chosen at random will get first class marks in the subject.

Answer

N/a

Explanation

Let `E_(1)=` event that a boy is selected.
`E_(2)=` event that a girl is selected.
and `E=` event that selected student will get first division.
`:. P(E_(1))=2/3,P(E_(2))=1/3`
`P(E//E_(1))=0.30,P(E//E_(2))=0.24`
Now from the total probability theorem
`P(E)=P(E_(1)).P(E//E_(1))+P(E_(2)).P(E//E_(2))`
`2/3xx0.30+1/3xx0.24`
`=0.20+0.08=0.28`