The probability of a bomb hitting a bridge is 1/2 and two direct hits ...
Let n ne the number of bombs required and X the number of bombs that hit the bridge.
Then X follows a bionomial distribution with parameters n and p=1/2. Now
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The probability of a bomb hitting a bridge is 1/2 and two direct hits ...
Answer:
To find the least number of bombs required to destroy the bridge with a probability greater than 0.9, we can use the concept of binomial distribution. Let's denote the probability of a bomb hitting the bridge as p = 1/2.
Calculating the probability:
To destroy the bridge, two direct hits are needed. The probability of getting exactly k direct hits out of n attempts is given by the binomial distribution formula:
P(k) = C(n, k) * p^k * (1-p)^(n-k)
Where C(n, k) represents the number of ways to choose k hits out of n attempts, and p^k * (1-p)^(n-k) represents the probability of getting exactly k hits.
We want to find the smallest value of n such that the probability of getting 2 or more direct hits is greater than 0.9. Therefore, we need to calculate the cumulative probability:
P(2 or more hits) = 1 - P(0) - P(1)
Calculating the smallest value of n:
To find the smallest value of n, we can start with n = 1 and increment it until the cumulative probability is greater than 0.9.
Let's calculate the cumulative probabilities for different values of n:
For n = 1:
P(0) = C(1, 0) * (1/2)^0 * (1-1/2)^(1-0) = 0
P(1) = C(1, 1) * (1/2)^1 * (1-1/2)^(1-1) = 1/2
P(2 or more hits) = 1 - P(0) - P(1) = 1 - 0 - 1/2 = 1/2
For n = 2:
P(0) = C(2, 0) * (1/2)^0 * (1-1/2)^(2-0) = 1/4
P(1) = C(2, 1) * (1/2)^1 * (1-1/2)^(2-1) = 1/2
P(2) = C(2, 2) * (1/2)^2 * (1-1/2)^(2-2) = 1/4
P(2 or more hits) = 1 - P(0) - P(1) = 1 - 1/4 - 1/2 = 1/4
For n = 3:
P(0) = C(3, 0) * (1/2)^0 * (1-1/2)^(3-0) = 1/8
P(1) = C(3, 1) * (1/2)^1 * (1-1/2)^(3-1) = 3/8
P(2) = C(3, 2) * (1/2)^2 * (1-1/2)^(3-2) = 3/8
P(3) = C(3, 3) * (1/2)^3 * (1-1/2)^(