Answer:
[tex]\dfrac{1}{7}[/tex]
Step-by-step explanation:
There are 7 days in a week.
For the first person, we select one day out of the 7 days. The first person has 7 options out of the 7 days.
Let Event A be the event that the first person was born on a day of the week.
Therefore:
[tex]P(A)=\dfrac{7}{7}=1[/tex]
The second person has to be born on the same day as the first person. Therefore, the second person has 1 out of 7 days to choose from.
Let Event B be the event that the second person was born.
Therefore, the probability that the second person was born on the same day as the first person:
[tex]P(B|A)=\dfrac{1}{7}[/tex]
By the definition of Conditional Probability
[tex]P(B|A)=\dfrac{P(B \cap A)}{P(A)} \\$Therefore:\\P(B \cap A)=P(B|A)P(A)[/tex]
The probability that both were born on the same day is:
[tex]P(B \cap A)=P(B|A)P(A) = \dfrac{1}{7} X 1 \\\\= \dfrac{1}{7}[/tex]
