$\begin{array}{1 1}(A)\;\large\frac{7}{128}\\(B)\;\large\frac{8}{122}\\(C)\;\large\frac{128}{7}\\(D)\;\large\frac{5}{128}\end{array} $

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- In a toos of coin getting head and Tail are equally likely
- P=P(H)=\(\large\frac{1}{2}\)
- q=1-P=1-\(\large\frac{1}{2}\)=\(\large\frac{1}{2}\)
- Tossed 10 times
- N=10
- X=\((0\;,1\;,2\;,3\;,4\;,5\;,6\;,7\;,8\;,9\;,10)\)
- P(X=r)=\(\large\;C^n_r \;P^r\; Q^{n-r}\)

P(at least 8 heads )=P(X=8)=P(X=9)+p(X=10)

\(C^{10}_8\;\Large(\frac{1}{2}\;)^8\;(\frac{1}{2}\;)^{10}+C^{10}_9\;(\frac{1}{2}\;)^9\;(\frac{1}{2}\;)^1+\;C^{10}_{10}(\frac{1}{2}\;)^{10}\;(\frac{1}{2}\;)^0\)

=(\(\Large\frac{1}{2}\))\(^{10}\times\)[45+10+1]

=(\(\frac{1}{2}\))\(^{10}\times\)56

=\(\frac{7}{128}\)

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