Latest TCS Aptitude Question SOLUTION: 3. What is ∑K=028K2(28KC) where 28KC is the number of ways of choosing k items from 28 items? a. 406 * 227 b. 306 * 226 c. 28 * 227 d. 56 * 227

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(#M40157582) TCS Numerical Ability question Keep an EYE

3. What is ∑K=028K2(28KC) where 28KC
is the number of ways of choosing k items from 28 items?
a. 406 * 227

b. 306 * 226

c. 28 * 227
d. 56 * 227

Asked In TCS lav (7 years ago)

Unsolved Read Solution (2)

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Read Solution (2) :

vamshi  (7 years ago)

Consider (1+x)n=C0+C1x+C2x2+.....+Cnxn .......(1)
Differentiating w.r.t x we get
n(1+x)n−1=C1+2C2x+3C3x2+.....+nCnxn−1
Multiplying by x on both sides,
x.n(1+x)n−1=x.C1+2C2x2+3C3x3+.....
Now again differentiating w.r.t to x
n(1+x)n−1+n(n−1)x(1+x)n−2=C0+22C1x+32C2x2+
42C3x3.....
Putting x = 1, we get
n(n+1)2n−2=C1+22C2+32C3+42C4
Now substituting n = 28
28(28+1)228−2 = 812.226 = 406.227

Is this solution Helpfull? Yes (5) | No (1)  

Rejaul Mallick  (7 years ago)

Did not get your answer.Please explain it bro Vamish

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