find the probability that a year chosen at random has 53 mondays .
"explanation : there are 2 kinds of year leap year - probability = 1 / 4 ( out of 4 years one is a leap year ) non leap year - probability = 3 / 4 so it ' s either this or that now in non leap year , there are 365 days meaning 52 weeks with one day extra that one day can be monday out of 7 possible days . hence the probability = 1 / 7 similarly in leap year , there are 366 days and so 366 / 7 = 52 weeks with 2 days extra now probability of occurrence of monday out of possible 7 days = 2 / 7 so what we essentially want is ( a non leap year and monday ) or ( a leap year and monday ) so it ' ll be [ 3 / 4 * 1 / 7 ] + [ 1 / 4 * 2 / 7 ] = 5 / 28 answer : a"
divide(const_2, add(const_3, const_4))