A fair coin is tossed a fixed number of times. If the probability of getting seven heads is equal to that of getting nine heads, the probability of getting two heads is a. `15/2^8` b. `2/15` c. `15/2^(13)` d. none of these

Explanation

Let `n` be the total number of tosses.


Let `X` be the number of times head occurs


`therefore p=1/2=q`


`Rightarrow \ ^n C_7 (1/2)^7 (1/2)^(n-7) = \ ^n C_9 (1/2)^9 (1/2)^(n-9)`


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