In month of December 31 daysi.e.(28+3)days. In 28 days will get 4 Sundays If we get any Sunday in first 3 days of December than only we can get 5 Sundays in month. n(5th Sunday)=3 [4 Weeks+3 days] n(5)=7 Hence prob.of 5 Sundays in month of December =