Q2 of 13 Page 283

1500 families with 2 children were selected randomly, and the following data were recorded:















Number of girls in a family



2



1



0



Number of families



475



814



211



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


(i) 2 girls


(ii) 1 girl


(iii) No girl


Also check whether the sum of these probabilities is 1.

Total number of families = 1500

(i) Numbers of families having two girls = 475


Probability of families having two girls will be,



(ii) Number of families having one girl = 814


Probability of families having one girl will be,



(iii) Number of families having zero girl = 211


Probability of families having zero girl will be,



Sum of probabilities



Hence,


Yes, the sum of these probabilities is 1.


More from this chapter

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1

In a cricket match, a batswoman hits a boundary 6 times out of 30 balls she plays. Find the probability that she did not hit a boundary.

 3

Refer to Example 5, Section 14.4, Chapter 14 Find the probability that a student of the class was born in August.

 4

Three coins are tossed simultaneously 200 times with the following frequencies of different outcomes:

















Outcome



3 heads



2 heads



1 head



No head



Frequency



23



72



77



28



If the three coins are simultaneously tossed again, compute the probability of 2 heads coming up

 5

An organisation selected 2400 families at random and surveyed them to determine a relationship between income level and the number of vehicles in a family. The information gathered is listed in the table below:




















Monthly income


(in Rs)



Vehicles per family



0



1



2



Above 2



Less than 7000


7000 – 10000


10000 – 13000


13000 – 16000


16000 or more



10


0


1


2


1



160


305


535


469


579



25


27


29


59


82



0


2


1


25


88



Suppose a family is chosen. Find the probability that the family chosen is


(i) Earning Rs 10000 – 13000 per month and owning exactly 2 vehicles.


(ii) Earning Rs 16000 or more per month and owning exactly 1 vehicle.


(iii) Earning less than Rs 7000 per month and does not own any vehicle.


(iv) Earning Rs 13000 – 16000 per month and owning more than 2 vehicles.


(v) Owning not more than 1 vehicle