If the probability that a flourescent light has a useful life of atleast 800 hours is 0.9,find the probabilities that among 20 such lights atleast 2 will not have a useful life of atleast 800 hours.

The probability that a bulb produced by a factory will fuse 150 days of use is 0.05.Find the probability that out of 5 such bulbs(iv)atleast one will fuse after 150 days of use.

The probability of hitting a target in any shot is 0.2.If 10 shots are fired,find the probability that the target will be hit atleast twice.

The probability that a mountain-bike rider travelling along a certain track will have a tyre burst is 0.05.Find the probability that among 17 riders:(i)exactly one has a burst type

The probability that a person who undergoes a kidney operation will recover is 0.7.Find the probability thatof the six patients who undergo similar operations.(iii)atleast hhalf of them will recover.

If probability of success in a single trail is 0.01.How many trails are required in order to have probability greater than 0.5 of getting atleast one success?

It is observed that,it rains on 12 days out of 30 days.Find the probability that (ii)it will rain on atleast 2 days of given week.

In a large school,80% of the pupils like mathematics.A visitor to the school asks each of 4 pupils,chosen at random,whether they like mathematics.(ii)Find the probability that the visitor obtains the answer yes from atleast 2 pupils:(a)when the number of pupils questioned remains at 4.(b)When the number of pupils questioned is increased to 8.