Question

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 a separate card, the cards being identical. Then she puts cards in a bag and stirs them thoroughly. She then draws one card from the bag. What is the probability that the name written on the card is the name of (i) a girl? (ii) a boy?

Answer 1

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

(i) The number of all possible outcomes is 40

The number of outcomes favourable for a card with the name of a girl = 25

Therefore, P (card with name of a girl) = P(Girl) =25/40=5/8

(ii) The number of outcomes favourable for a card with the name of a boy = 15 

Therefore, P(card with name of a boy) = P(Boy) =15/40=3/8

Note: We can also determine P(Boy), by taking

P(Boy) = 1 – P(not Boy) = 1 – P(Girl) =1-5/8=3/8