Originally Posted by

**gkraju** In the question, mean was not stated directly i think we have to find the answer assuming mean to be zero.

i have no clue how to go ahead with it, i tried this way, assuming mean to be zero,

calculating z = (X- mean)/ std deviation, i.e. z = 10-0/10 = 1.

then i calculate area under the normal curve between -1 to 1.

now i get the probability of bomb hitting target with in + or - 10 metres, this is for population of 3000 bombs.

i am struck here, how to make this probability which i got for 3000 bombs to be applicable for getting

50bombs withi in 10 metres out of 80 bombs ?

please help me out.