Question 18

An unbiased dice is tossed seven times. Find the probability of getting a third six on the seventh throw.

Solution

We need a third 6 in the 7th throw which means that in the first 6 throws we should get 6 exactly twice.

No. of ways of getting 6 exactly twice in first 6 throws= $$^6C_2$$

Probability of getting 6 for the third time in the seventh throw= $$\frac{\left(^6C_2\times\ 5^4\right)}{6^7}$$


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