Question

In a class, there are 18 girls and 16 boys. The class teacher wants to choose one for class monitor. What she does she writes the name of each on a card and puts them into a basket and mixes throoughly? A child is asked to pick up on card from the basket. What is the probability that the name written on the card is (i) the name of a girl? (ii) the name of a boy? (iii) the name of topper student of the class? (iv) not 'Shiv Kumar' who is the son of Principal of this school?

Answer 1

(i) Total number of elementary events = total number of girls and boys = 18 + 16 =34
`therefore "Probability that the name written on the card is the name of a girl "=("Favourable number of elementary events")/("Total number of elementary events")=(18)/(34)=(9)/(17)`
(ii) Probability that the name written on the card is the name of a boy `=("Favourable number of elemantary events")/("Total number of elementary events")=(16)/(34)=(18)/(17)`
(iii) Topper of class is only one particular student.
`therefore` Favourable number of elementary event = 1
`therefore "Required probability "=("Favourable number of elementry events")/("Total number of elementary events")=(1)/(34)`
(iv) We do not want that name written on the card is Shiv Kumar. So, name written on the card may be of any other student except Shiv Kumar.
`therefore` Favourable number of elementary events = 33
`therefore "Required probability "=(33)/(34)`