The value of sum_{k=0}^{10} C(10,k) * 2^k is _________.

GATE 2015 · Discrete Mathematics · Summation · medium

Answer: sum_{k=0}^{10} C(10,k) * 2^k = 3^10 = 59049.

  1. Recognise the binomial template: Set n=10, x=1, y=2. Right side becomes sum_{k=0}^{10} C(10,k) * 1^(10-k) * 2^k = sum_{k=0}^{10} C(10,k) * 2^k, which is exactly the given expression.
  2. Evaluate the left side: Left side with x=1, y=2: (1+2)^10 = 3^10.
  3. Compute 3^10: 3^1=3, 3^2=9, 3^3=27, 3^4=81, 3^5=243, 3^6=729, 3^7=2187, 3^8=6561, 3^9=19683, 3^10=59049.