Please explain: 99. A fair coin is tossed n times. If the probability of getting 7 heads is equal to the probability of getting 9 heads, then the value of n will be. (a) 8 (b) 13 (c) 15 (d) None of these. Share with your friends Share 0 Aarushi Mishra answered this Tossing a fair coin n times is a binomial distribution with probability of success, p=12Pr successes=PX=r=Crn pr 1-pn-rGiven PX=7=PX=9C7n 127 1-12n-7=C9n 129 1-12n-9C7n 127 12n-7=C9n 129 12n-9C7n 12n-7+7=C9n 12n-9+9C7n 12n=C9n 12nC7n=C9nUsing Crn=Cn-rnC7n=Cn-9nComparing7=n-9n=16 1 View Full Answer Adithi N. Prabhu answered this P(X=7) = P(X=9)nC7 (1/2)7 (1/2)n-7 = nC9 (1/2)9 (1/2)n-9 thus, n=16 so according to your question, answer is option D! (none of these)Hope this helps :)-A 1
