Question

Five horses are in a race. Mr. $$A$$ selects two of the horses at random and bets on them. The probability that Mr. $$A$$ selected the winning horse is

A. $$\frac{2}{5}$$  
B. $$\frac{4}{5}$$
C. $$\frac{3}{5}$$
D. $$\frac{1}{5}$$
Answer :   $$\frac{2}{5}$$
Solution :
Let 5 horses are $${H_1},$$ $${H_2},$$ $${H_3},$$ $${H_4},$$ and $${H_5}.$$ Selected pair of horses will be one of the 10 pairs $$\left( {{\text{i}}{\text{.e}}{\text{.;}}{{\text{ }}^5}{C_2}} \right):{H_1}{H_2},$$     $${H_1}{H_3},$$   $${H_1}{H_4},$$   $${H_1}{H_5},$$   $${H_2}{H_3},$$   $${H_2}{H_4},$$   $${H_2}{H_5},$$   $${H_3}{H_4},$$   $${H_3}{H_5},$$   and $${H_4}{H_5}.$$
Any horse can win the race in 4 ways.
For example : Horses $${H_2}$$ win the race in 4 ways $${H_1}{H_2},$$   $${H_2}{H_3},$$   $${H_2}{H_4},$$   and $${H_2}{H_5}.$$
Hence required probability $$ = \frac{4}{{10}} = \frac{2}{5}$$

Releted MCQ Question on
Statistics and Probability >> Probability

Releted Question 1

Two fair dice are tossed. Let $$x$$ be the event that the first die shows an even number and $$y$$ be the event that the second die shows an odd number. The two events $$x$$ and $$y$$ are:

A. Mutually exclusive
B. Independent and mutually exclusive
C. Dependent
D. None of these
Releted Question 2

Two events $$A$$ and $$B$$ have probabilities 0.25 and 0.50 respectively. The probability that both $$A$$ and $$B$$ occur simultaneously is 0.14. Then the probability that neither $$A$$ nor $$B$$ occurs is

A. 0.39
B. 0.25
C. 0.11
D. none of these
Releted Question 3

The probability that an event $$A$$ happens in one trial of an experiment is 0.4. Three independent trials of the experiment are performed. The probability that the event $$A$$ happens at least once is

A. 0.936
B. 0.784
C. 0.904
D. none of these
Releted Question 4

If $$A$$ and $$B$$ are two events such that $$P(A) > 0,$$   and $$P\left( B \right) \ne 1,$$   then $$P\left( {\frac{{\overline A }}{{\overline B }}} \right)$$  is equal to
(Here $$\overline A$$ and $$\overline B$$ are complements of $$A$$ and $$B$$ respectively).

A. $$1 - P\left( {\frac{A}{B}} \right)$$
B. $$1 - P\left( {\frac{{\overline A }}{B}} \right)$$
C. $$\frac{{1 - P\left( {A \cup B} \right)}}{{P\left( {\overline B } \right)}}$$
D. $$\frac{{P\left( {\overline A } \right)}}{{P\left( {\overline B } \right)}}$$

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Probability


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