If a person purchases 15 of the 3,000 tickets sold in a...

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swerve: Legendary Member; Posts: 2499; Joined: Sun Oct 29, 2017 2:04 pm; Followed by:6 members

If a person purchases 15 of the 3,000 tickets sold in a...

by swerve » Wed Jan 31, 2018 5:33 am

If a person purchases 15 of the 3,000 tickets sold in a raffle that awards one prize, what is the probability that this person will not win?

A. 0
B. 1/200
C. 1/2
D. 199/200
E. 1

The OA is D.

Please, can any expert explain this PS question for me? I tried to solve it but I can't get the correct answer.

I know that the probability that this person will win is 15/3000, but how can I determine the probability that this person will not win?. I need your help. Thanks.

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Source: Beat The GMAT — Problem Solving | Wed Jan 31, 2018 5:33 am

DrMaths: Senior | Next Rank: 100 Posts; Posts: 82; Joined: Mon Jan 15, 2018 2:01 am

by DrMaths » Wed Jan 31, 2018 7:50 am

If a person purchases 15 of the 3,000 tickets sold in a raffle that awards one prize, what is the probability that this person will not win?

A. 0
B. 1/200
C. 1/2
D. 199/200
E. 1

Two solutions, same answer:

(1) Pure method:

P = P(winning ) = 15/3000 = 5/1000 = 1/200
P' = (P of not winning) = 1 - P = 1 - 1/200 = 199/200

(2) Looking at the given answers:

A. 0 - It is not impossible to lose!
B. 1/200 - A disproportionately small value!
C. 1/2 - It's clearly not an even chance!
D. 199/200 - is a reasonable figure
E. 1 - It is not certain to lose!

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EconomistGMATTutor: GMAT Instructor; Posts: 555; Joined: Wed Oct 04, 2017 4:18 pm; Thanked: 180 times; Followed by:12 members

by EconomistGMATTutor » Wed Jan 31, 2018 11:10 am

If a person purchases 15 of the 3,000 tickets sold in a raffle that awards one prize, what is the probability that this person will not win?

A. 0
B. 1/200
C. 1/2
D. 199/200
E. 1

The OA is D.

Please, can any expert explain this PS question for me? I tried to solve it but I can't get the correct answer.

I know that the probability that this person will win is 15/3000, but how can I determine the probability that this person will not win?. I need your help. Thanks.

Hi swerve,
Let's take a look at your question.

We know that we can find the probability of an event by dividing the number of successful outcomes divided by the total number of outcomes.
Number of tickets purchased by a person = 15
Total number of tickets = 3000

We will first find the probability of winning.
$$P\left(\text{The person will win}\right)=\frac{15}{3000}=\frac{1}{200}$$

Now, we can find the probability that the person will not win just by subtracting the above probability from 1.
$$P\left(\text{The person will not Win}\right)=1-\frac{1}{200}=\frac{200-1}{200}=\frac{199}{200}$$

Therefore, Option D is correct.

Hope it helps.
I am available if you'd like any follow up.

GMAT Prep From The Economist
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GMAT/MBA Expert

Scott@TargetTestPrep: GMAT Instructor; Posts: 8086; Joined: Sat Apr 25, 2015 10:56 am; Location: Los Angeles, CA; Thanked: 43 times; Followed by:29 members

by Scott@TargetTestPrep » Fri Feb 02, 2018 11:13 am

swerve wrote:If a person purchases 15 of the 3,000 tickets sold in a raffle that awards one prize, what is the probability that this person will not win?

A. 0
B. 1/200
C. 1/2
D. 199/200
E. 1

The probability of not winning is (3,000 - 15)/3,000 = 2,985/3,000 = 597/600 = 199/200.

Alternate solution:

The probability of winning is 15/3,000 = 1/200; thus the probability of not winning is 1 - 1/200 = 199/200.

Answer: D

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