71\textup{i.e.,}\sum_{i=0}^{2m}{^{4m}C_{2m+i}}
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Q) A student attends an exam carrying four sets of question papers , each set carrying m questions with equal marks alloted. To qualify the exam, he needs to get 2m questions correct. In how many ways can he qualify the exam ?
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9 Answers
1The student succeds if gets 2m or more than 2m ans correct..
So the no of possible ways
4mC2m + 4mC(2m+1) + 4mC(2m+2) + ..... 4mC4m
71
1By Multinomial Theorem
Look for the coefficient of x2m in (x0+x1+x2+......xm)4
1@satyaki well i dont think ur ans is correct for this sum
becoz what u have found out is the no of ways he can get 2m correct..not the no of ways he can qualify(coz he will qualify if he gets any no of qusetion correct >2m)
in order to find that u need to find the coefficient of x2m,x2m+1,x2m+2... in the expression..
and u wud end up with the same result that i have given here..
1@aieee
koi short ans dia hai[like i gave above] ya expansion di hai...
pls tell..