Question

Fifteen coupons are numbered 1, 2, … 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. (9/10)⁶
• B. (8/15)⁷
• C. (3/5)⁷
• D. None

Answer 1

Answer: (C)

(3/5)⁷

Answer 2

For one trial, n(S) = 15, E = {1, 2, 3,…9}

∴ n(5) = 9

Since seven trials are performed with replacement and all are independent, therefore

Required probability = $\left( \frac { 9 } { 15 } \right) ^ { 7 } = \left( \frac { 3 } { 5 } \right) ^ { 7 }$