A fair coin is tossed ten times. What is the probability of getting at least two heads?
Explanation
To solve this, we need to find the probability of getting at least two heads when a fair coin is tossed 10 times.
The easiest way to do this is to first calculate the probability of getting 0 or 1 head, and then subtract that from 1 to get the probability of getting at least two heads.
The probability of getting exactly \( k \) heads in \( n \) tosses of a fair coin follows the binomial distribution:
\[
P(X = k) = \binom{n}{k} \times p^k \times (1 - p)^{n - k}
\]
where:
- \( n = 10 \) (number of tosses),
- \( p = 0.5 \) (probability of getting a head on any toss),
- \( k \) is the number of heads.
1. Probability of getting 0 heads:
\[
P(X = 0) = \binom{10}{0} \times (0.5)^0 \times (0.5)^{10} = 1 \times 1 \times \frac{1}{1024} = \frac{1}{1024}
\]
2. Probability of getting 1 head:
\[
P(X = 1) = \binom{10}{1} \times (0.5)^1 \times (0.5)^9 = 10 \times \frac{1}{2} \times \frac{1}{512} = \frac{10}{1024}
\]
So, the total probability of getting 0 or 1 head is:
\[
P(X = 0 \text{ or } 1) = \frac{1}{1024} + \frac{10}{1024} = \frac{11}{1024}
\]
Now, subtract this from 1 to find the probability of getting at least two heads:
\[
P(\text{at least 2 heads}) = 1 - \frac{11}{1024} = \frac{1024 - 11}{1024} = \frac{1013}{1024}
\]