Find the probability that a leap year will have 53 Friday or 53 Saturdays.

Options

A. `(2)/(7)`
B. `(3)/(7)`
C. `(4)/(7)`
D. `(1)/(7)`

Answer

B

Explanation

In a leap year, there are 366 days in which 52 weeks and two days. The combination of two days may be : Sun-Mon, Mon-Tue, Tue-Wed, Wed-Thur, Thur-Fri, Fri-Sat, Sat-sun.
`P(53Fri)=(2)/(7), P(53Sat)=(2)/(7)`
One combination is common, i.e. (Fri-Sat)
`therefore P(53 Fri and 53 Sat)= (1)/(7)`
`therefore P(53 Fri or Sat)=P(53 Fri)+P(53 Sat)-P(53 Fri and Sat)`
`=(2)/(7)+(2)/(7)-(1)/(7)=(3)/(7)`