(Q28) There are 40 students in Class X of a school of whom 25 are girls and 15 are boys. The class teacher has to select one student as a class representative. She writes the name of each student on separate cards, the cards being identical. Then she puts cards in a box and stirs them thoroughly. She then draws one card from the box. What is the probability that the name written on the card is the name of (i) a girl? (ii) a boy?

Solution :

There are 40 students, and only one name card has to be chosen.

The number of all possible outcomes is .

(i) The number of outcomes favourable for a card with the name of a girl =

  ∴ P (card with name of a girl) = P(Girl) =

=

5

(ii) The number of outcomes favourable for a card with the name of a boy = .