Question

Let $S = ${1, 2, ...... , 20}. A subset $B$ of $S$ is said to be "nice", if the sum of the elements of $B$ is $203$. Then the probability that a randomly chosen subset of $S$ is "nice" is :

• A. $\frac{6}{2^{20}}$
• B. $\frac{5}{2^{20}}$
• C. $\frac{4}{2^{20}}$
• D. $\frac{7}{2^{20}}$

Answer 1

Answer: (B)

7,
1,6
2,5
3,4
1,2,4
$P = \frac{5}{2^{20}}$