probability q (1 Viewer)

[spagbowl]

i can't for the life of me remeber how to use probability to answer this question:

The probability that advertisements are showing when changing tv channels at rndom is 2/5. If George changes channels 6 times during an evening, find the probabilty that advertisements are showing
a) on 2 occasions
b) more than 4 times

Thanks heaps

 

[Timothy.Siu]

i can't for the life of me remeber how to use probability to answer this question:

The probability that advertisements are showing when changing tv channels at rndom is 2/5. If George changes channels 6 times during an evening, find the probabilty that advertisements are showing
a) on 2 occasions
b) more than 4 times

Thanks heaps

i'll assume he doesn't start on an ad.

a) 6C2.(2/5)^2 . (3/5)^4

b) so 5 or 6 times
6C5.(2/5)^5.(3/5)+6C6.(2/5)^6