Question 1155291
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It is  P = {{{sum(C[30]^k*0.6^k*0.4^(30-k),k=18,30)}}} = 1 - {{{sum(C[30]^k*0.6^k*0.4^(30-k),k=1,17)}}} = 1 - BINOM.DIST(17,30,0.6,TRUE) = 1 - 0.4215 = 0.5785.    <U>ANSWER</U>


I used the probability 0.6 to guess correctly and 0.4 to guess incorrectly (according to the condition)
</pre>

Solved.


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I used Excel function  BINOM.DIST to quickly calculate the expression.


On Excel function BINOM.DIST, see its description everywhere, for example


https://support.office.com/en-us/article/binom-dist-function-c5ae37b6-f39c-4be2-94c2-509a1480770c