Question of The Day25-11-2019

An unbiased coin is tossed seven times in a row, what is the probability of getting at least one head if on the first toss came the tail?

Correct Answer : a ) $$63 \over 64$$

Explanation :

If on the first toss, the tail came, then there will be only 6 tosses remaining.

As the coin is unbiased, so there is a fair chance of getting a head and tail.

So, the total possible outcomes will be = 26 = 64

Thus, the number of outcomes on which no head came will be = 1

As we know that

Probability of getting no head if on the first toss tail came =$$1 \over 64$$

Therefore, probability of getting at least one head if on the first toss tail came = (1 – Probability of getting no head if on the first toss tail came)

$$=>{1-{1\over64}}={63\over64}$$

Hence, (A) is the correct answer.

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