What is Σk=0 to 28 k^2(28 C k ), where (28C k) is the number of ways of choosing k items from 28 items?
a. 406 *2^27
b. 306 *2^26
c. 28 *2^27
d. 56 *2^27

• (0+1+2+3+......+28)^2((28 C 0)+(28 C 1)+.....+(28 C 28)) we know that
  (n C 0)+(n C 1)+.......+(n C n)=2^n and (1+2+....+n)=(n(n+1))/2
  so,
  (0+1+2+...+28)=(28(28+1))/2=406
  and (28 C 0)+(28 C 1)+...+(28 C 28)=2^28
  2 * (2^28)=2^27
  finally answer is 406 * 2^27
• 10 years agoHelpfull: Yes(11) No(2)
• The answer may be 28*2^27 because the no. of ways of choosing k 28 and the k value is from 0-28 i.e) 27 numbers...
  by the formula (2a)^n we can solve it
• 10 years agoHelpfull: Yes(1) No(2)
• please solve the ques and explain it..
  
• 10 years agoHelpfull: Yes(0) No(1)
• 56*2^27 formula is 2a^n a=28 and n=27
  28 items...
• 10 years agoHelpfull: Yes(0) No(1)
• (((28)(28+1)(2(28)+1))/6) * 2^28
• 10 years agoHelpfull: Yes(0) No(0)
• (0+1+2+3+4+5..........+28)=(n/2(first term + last term)
  (29/2)(0+28)=406/2
  now
  28C0+28C1+28C2+28C3.................28C28=2^28
  (406/2)(2^28)=406*2^27
• 10 years agoHelpfull: Yes(0) No(0)