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A discount coupon is distributed to N riders, and the likelihood of utilizing a coupon is P. What is the probability that at least one coupon will be used?

Approach / Explanation

This question presents two variables. N riders - This denotes the total number of coupons that have been distributed or are available for use. Probability of using a coupon, P - This indicates the likelihood that any individual coupon will be utilized. The inquiry seeks to determine the probability that at least one of the N coupons will be used, assuming each rider has the same probability (P) of utilizing their coupon. It is important to note that the riders operate independently, meaning that one rider’s use of a coupon does not influence another rider's choice to use theirs. The crucial aspect of answering this question is recognizing that the probability of at least one occurrence is equal to 1 minus the probability of none occurring.

Suggested Answer

To determine this, you should first calculate the probability that none of the coupons are used and then subtract that result from one. The probability that a single coupon is not used is (1-P), meaning that for N coupons, the probability of none being used is (1-P)^N. Consequently, the probability that at least one coupon is used is 1 - ((1-P)^N).

Alternative Answer

To solve this type of probability question, we focus on the principle of '1 minus the probability of the complement'. Here, the 'complement' refers to the scenario where none of the coupons are utilized. The probability that a single coupon is not used is (1-P), which means that for N coupons, the probability is (1-P) raised to the Nth power. By subtracting this value from 1, we determine that the probability of at least one coupon being used is 1 - (1-P)^N.

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Medium

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Lyft

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