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Question

Out of 6 unbiased coins, 5 are tossed independently and they all result in heads. If the 6$^\text{th}$ is now independently tossed, the probability of getting head is

The correct answer is
1/2

Probability of Independent Coin Toss

The question asks for the probability of getting a head when the 6th coin is tossed.

  • We are given 6 unbiased coins.
  • The first 5 coins were tossed independently and resulted in heads.
  • The 6th coin is now tossed independently.

Key Principle: For unbiased coins, each toss is an independent event. The outcome of previous tosses (the first 5 coins) has no influence on the outcome of the 6th toss.

Since the 6th coin is unbiased:

  • The probability of getting a head ($P(H)$) is equal to the probability of getting a tail ($P(T)$).
  • Mathematically, $P(H) = P(T) = \\frac{1}{2}$.

Therefore, the probability of getting a head on the 6th independent toss is $\\frac{1}{2}$.

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Important Questions from Probability (Notes)

  1. A stick of length L is broken into two pieces at random. What is the average length of the smaller piece?
  2. Two students are solving the same problem independently. If the probability that the first one solves the problem is $\frac{3}{5}$ and the probability that the second solves the problem is $\frac{4}{5}$, what is the probability that at least one of them solves the problem?
  3. A fair die was thrown three times and the outcome was repeatedly six. If the die is thrown again what is the probability of getting six?
  4. A canal system is shown in the figure. 

    Water flows from A to B through two channels. Gates $G_1$ and $G_2$ are operated independently to regulate the flow. Probability of $G_1$ to be open is 10% while that of $G_2$ is 20%. The probability that water will flow from A to B is

  5. A standard fair die is rolled until some face other than 5 or 6 turns up. Let $X$ denote the face value of the last roll, and $A = \{X \text{ is even}\}$ and $B = \{X \text{ is at most 2}\}$. Then,
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