Question

Assume that on a week day one telephone number out of every ten being called is busy.If 6 randomly selected numbers are called what is the probability that at least three of them will be busy?

Answer 1

the probability that at least three of them will be busy is equal to=>C(6,3)*(1/10)^3 *(9/10)^3 + C(6,4) *(1/10)^4 *(9/10)^2 + ... + C(6,6) *(1/10)^6

Answer 2

Given :⇒Probability ( Busy telephone numbers ) = 1 / 10. ..........! ⇒Probability ( Not busy telephone numbers ) = 9 / 10. ...............! According to the given question. ..............! To find :⇒ Probability (at least 3 of 6 are busy) = ?.................................! Sol :- Probability ( at least 3 of 6 are busy) = P ( Busy telephone numbers) /P ( Not busy telephone numbers ). ......= (1/ 10 )/(( 9/10)..= so , Probability ( at least 3 of 6 are busy) = C(6,3)(1/10)² 3 (9/(10²)3) + C(6,4) (1/10)²4 (9/10)²2 + ... + C(6,6) (1/10)² ..is the answer !