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10 coins. 9 are fair and one is double-headed. (1). Randomly choose a coin, flip it, and put it back. What's the probability of getting 5 heads in 5 flips? (2). Now the coins will not be put back after each flip. What's the probability of getting 5 heads in 5 flips?

User Bronson
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2 Answers

1 vote

Final answer:

The probability of getting 5 heads in 5 flips when the coins are put back after each flip is 3.125%, and the probability of getting 5 heads in 5 flips without replacement is 16.25%.

Step-by-step explanation:

The probability of getting 5 heads in 5 flips when the coins are put back after each flip can be calculated using the binomial probability formula.

The formula is P(X=k) = C(n, k) * p^k * (1-p)^(n-k), where n is the number of flips, k is the number of heads, and p is the probability of getting a head on each flip. In this case, n=5, k=5, and p=0.5.

Plugging these values into the formula gives:

P(X=5) = C(5, 5) * 0.5^5 * (1-0.5)^(5-5) = 1 * 0.5^5 * 0.5^0 = 0.5^5 = 0.03125, or 3.125%

When the coins are not put back after each flip, the probability changes because the outcome of each flip affects the subsequent flips.

To calculate the probability of getting 5 heads in 5 flips without replacement, we need to use a different approach.

Since there is only one double-headed coin, the probability of selecting it is 1/10, and the probability of selecting a fair coin is 9/10.

Once a coin is selected, the probability of getting a head on that coin is 1 for the double-headed coin and 0.5 for the fair coin.

We can calculate the probability of getting 5 heads in 5 flips without replacement by considering all possible ways of selecting the coins:

P(5 heads in 5 flips) = P(1 double-headed coin, 5 heads) + P(2 double-headed coins, 3 heads) + P(3 double-headed coins, 1 head)

P(5 heads in 5 flips) = (1/10) * (1^5) * (9/10)^4 + (1/10) * (1^3) * (9/10)^2 + (1/10) * (1^1) * (9/10)^0 = 0.1625, or 16.25%

User Karim Harazin
by
5.0k points
5 votes

Good evening ,

Answer:

(1) the probability of getting 5 heads in 5 flips = (9/10)⁵

(2) the probability of getting 5 heads in 5 flips = (9×8×7×6×5)÷(10×9×8×7×6) = 0,5.

:)

User Sebyddd
by
5.5k points
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