80 bulbs are selected at random from a lot and their life time (in hours) is recorded in the form of a frequency table given below : Life time (in hours) Frequency 300 10 500 12 700 23 900 25 1100 10 One bulb is selected at random from the lot. What is the probability that its life is less than 900 hours ?

80 bulbs are selected at random from a lot and their life time (in hrs) is recorded in the form of a frequency table given below : Life time (in hours) Frequency 300 10 500 12 700 23 900 25 1100 10 According to given frequency table number of bulbs, having life-time less than 900 hours = 10 + 12 + 23 = 45 Total number of bulbs = 10 + 12 + 23 + 25 + 10 = 80 We know that, probability P E = Number of favourable outcomes Total Number of trials P 900 = N u m b e r o f b u l b s h a v i n g t h e l i f e t i m e o f 900 hour s T o t a l n u m b e r o f b u l b s = 45 80 = 9 16 So, probability of selecting a bulb which have a life-time of less than 900 hours = 9 16 = 0. 56 .