Three electric lamps are fitted in a room.  3 bulbs are chosen at random from 10 bulbs having 6 good bulbs. The probability that the room is lighted is

There are 10 bulbs in which 6 are good, means 4 are not good P(Room lighted) = 1−P(Room is not lighted)                                    =1−4C310C3                                   = 1−130 = 2930∴ The probability that the room is lighted is  2930