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14.Probability
medium
In a relay race there are five teams $A, \,B, \,C, \,D$ and $E$. What is the probability that $A, \,B$ and $C$ finish first, second and third, respectively.
A
$\frac{1}{60}$
B
$\frac{1}{60}$
C
$\frac{1}{60}$
D
$\frac{1}{60}$
Solution
If we consider the sample space consisting of all finishing orders in the first three places, we will have $^{5} P _{3},$ i.e., $, \frac{5 \,!}{(5-3) \,!}$ $=5 \times 4 \times 3=60$ sample points, each with a probability of $\frac{1}{60}$.
$A,\, B$ and $C$ finish first, second and third, respectively. There is only one finishing order for this, i.e., $ABC$.
Thus $P( A ,\, B$ and $C$ finish first, second and third respectively $)$ $=\frac{1}{60}$
Standard 11
Mathematics
