Q9 of 24 Page 97

2000 families with 2 children were selected randomly, and the following data were recorded.


Find the probability of a family, chosen at random, having


(i) 2 girls (ii) 1 girl (iii) no girl

Let having 2 girls be Event E1

Having 1 girl be event E2


Having no girl be Event E3


(i) (∵ no. of families with 2 girls is 624 among a total of 2000 families)


⇒


(ii) (∵ no. of families with 1 girl is 900 among a total of 2000 families)


⇒


(iii) (∵ no. of families with 0 girl is 476 among a total of 2000 families)


⇒


More from this chapter

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7

In the sample of 50 people, 21 has type “O” blood, 22 has type “A” blood, 5 has type “B” blood and 2 has type “AB” blood. If a person is selected at random find the probability that

(i) the person has type “O” blood (ii) the person does not have type “B” blood


(iii) the person has type “A” blood (iv) the person does not have type “AB” blood.

 8

A die is rolled 500 times. The following table shows that the outcomes of the die.


Find the probability of getting an outcome (i) less than 4


(ii) less than 2


(iii) greater than 2 (iv) getting 6 (v) not getting 6.

 10

The following table gives the lifetime of 500 CFL lamps.


A bulb is selected at random. Find the probability that the life time of the selected bulb is


(i) less than 12 months (ii) more than 14 months


(iii) at most 12 months (iv) at least 13 months

 11

On a busy road in a city the number of persons sitting in the cars passing by were observed during a particular interval of time. Data of 60 such cars is given in the following table.


Suppose another car passes by after this time interval. Find the probability that it has


(i) only 2 persons sitting in it (ii) less than 3 persons in it


(iii) more than 2 persons in it (iv) at least 4 persons in it