Statistics problem

[hamizahmed]

can someone xplain me ques 7 part 2 of june 2004

 

[weesha]

probability of getting at least one damaged tape means 1,2,...,n tapes but not zero...
so 1 - p(o) = 0.85
p(0) = nC0 (0.2)^0 (0.8)^n
it becomes 1 - 0.8^n = 0.85
now solve it to get the value of n

 

[hamizahmed]

thnx mate

 

[hamizahmed]

and can anyone explain me ques 6 of nov 04. Just couldnot undrstand when will we cum to knw that our all the possibilities have been listed down?? I just hate such type of ques

 

[weesha]

for that make use of nCr and nPr formulas..
out of 5 u have to make differnt combinations of 3
5C3 is 10
by doing this u would at least know k how many combos have to be made...
dat what i do for such questions

 

[hamizahmed]

thnks yar