Question

Fifteen coupons are numbered 1 to 15. Seven coupons are selected at random, one at a time with replacement. The probability that the largest number appearing on a selected coupon be 9, is:




None of these

Answer 1

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Answer 2

The probability of the largest number appearing on a selected coupon be 9, is (9'7 - 8'7)/15'7

Total number of coupons = 15 (Given)

Number of selected coupons = 7 (Given)

Let the probability that a selected coupon bears number <9 be = p

Thus, p = 9/15  

Total number of ways as to how coupon can be drawn = 15'7

Now, According to the question 7 coupons must be selected numbered from 1 to 9 such that 9 it is selected at least once.

Total number of favourable ways = 9'7 - 8'7

Therefore,

Required probability = (9'7 - 8'7)/15'7