The probability of a leap year selected randomly having 53 Sundays can be calculated by dividing the number of favorable outcomes by the total number of possible outcomes. A leap year has 366 days or 52 weeks and 2 odd days. The two odd days can be {Sunday, Monday}, {Monday, Tuesday}, {Tuesday, Wednesday}, {Wednesday, Thursday}, {Thursday, Friday}, {Friday, Saturday}, {Saturday, Sunday}. So there are 7 possibilities out of which 2 have a Sunday. Therefore, the probability of a leap year selected randomly having 53 Sundays is 2/7.