1.

Fifteen coupens are numbered `1,2,3,...15` respectively. Seven coupons are selected at random one at a time with replacement The Probability that the largest number appearing on a selected coupon is 9 is :A. `((9)/(196))^(6)`B. `((8)/(15))^(7)`C. `((3)/(7))^(7)`D. None of these

Answer» Correct Answer - D
Since, there are 15 possible cases for selecting a coupor and seven coupons are selected, the total number o cases of selecting seven coupons =`15^7`
It is given that the maximum ·number on the selecte coupon is 9, therefore the selection is to be made from the coupons numbered 1 to 9. This can be made in r ways. Out of these `9^7` cases `8^7` does not contain the number 9.
Thus, the favourable number of cases `=9^7-8^7`
`therefore` Required probability `=(9^7-8^7)/(15^7)`


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