CBSE Class 10-Mathematics: Chapter –15 Probability Part 18

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Question 2:

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?

Answer:

(i) The outcomes associated with the experiment in which a dice is thrown is twice:

Therefore, Total number of favourable outcomes

Now consider the following events:

first throe shows and second throw shows

Therefore, the number of favourable outcomes in each case.

Required probability

(ii) Let S be the sample space associated with the random experiment of throwing a die twice. Then,

first and second throw shoe , i.e. getting in each throw.

We have,

And

Required probability = Probability that at least one of the two throws shows 5

Question 3:

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?

Answer:

Total favourable outcomes associated to the random experiment of visiting a particular shop in the same week (Tuesday to Saturday) by two customers Shyam and Exta are:

Total number of favourable outcomes

(i) The favourable outcomes of visiting on the same day .

Number of favourable outcomes

Hence required probability

(ii) The favourable outcomes of visiting on consecutive days are

Number of favourable outcomes

Hence required probability

(iii) Number of favourable outcomes of visiting on different days are

Number of favourable outcomes

Hence required probability