Q24 of 31 Page 308

A die is thrown twice. What is the probability that

(i) 5 will not come up either time?


(ii) 5 will come up at least once?


[Hint: Throwing a die twice and throwing two dice simultaneously are treated as the same experiment]

Total number of outcomes = 6 × 6

= 36


(i)Total number of outcomes when 5 comes up on either time are (5, 1), (5, 2), (5, 3), (5, 4), (5, 5), (5, 6), (1, 5), (2, 5),


(3, 5), (4, 5), (6, 5)


Therefore, the total number of favourable cases = 11


P (5 will come up either time) =


P (5 will not come up either time) = 1 -


=


(ii)Total number of cases, where 5 comes at least once = 11


P (5 will come at least once) =


=


More from this chapter

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22

Refer to Example 13. (i) Complete the following table:































Event : ‘Sum on 2 dice’



2



3



4



5



6



7



8



9



10



11



12



Probability



1/36








5/36






1/36



(ii) A student argues that ‘there are 11 possible outcomes 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and12. Therefore, each of them has a probabilityDo you agree with this argument? Justify your answer

 23

A game consists of tossing a one rupee coin 3 times and noting its outcome each time. Hanif wins if all the tosses give the same result i.e., three heads or three tails, and loses otherwise. Calculate the probability that Hanif will lose the game

 25

Which of the following arguments are correct and which are not correct? Give reasons for your answer.

(i) If two coins are tossed simultaneously there are three possible outcomes—two heads, two tails or one of each. Therefore, for each of these outcomes, the probability is


(ii) If a die is thrown, there are two possible outcomes—an odd number or an even number. Therefore, the probability of getting an odd number is

 1

Two customers Shyam and Ekta are visiting a particular shop in the same week (Tuesday to Saturday). Each is equally likely to visit the shop on any day as on another day. What is the probability that both will visit the shop on

(i) The same day?


(ii) Consecutive days?


(iii) Different days?