Last visit was: 23 Apr 2026, 05:06 It is currently 23 Apr 2026, 05:06
Close
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Close
Request Expert Reply
Confirm Cancel
User avatar
SergejK
Joined: 22 Mar 2024
Last visit: 02 May 2025
Posts: 152
Own Kudos:
977
 [35]
Given Kudos: 74
Posts: 152
Kudos: 977
 [35]
2
Kudos
Add Kudos
33
Bookmarks
Bookmark this Post
Most Helpful Reply
User avatar
MartyMurray
Joined: 11 Aug 2023
Last visit: 23 Apr 2026
Posts: 1,843
Own Kudos:
7,097
 [6]
Given Kudos: 212
GMAT 1: 800 Q51 V51
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
GMAT 1: 800 Q51 V51
Posts: 1,843
Kudos: 7,097
 [6]
6
Kudos
Add Kudos
Bookmarks
Bookmark this Post
General Discussion
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 23 Apr 2026
Posts: 109,776
Own Kudos:
810,757
 [4]
Given Kudos: 105,853
Products:
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 109,776
Kudos: 810,757
 [4]
3
Kudos
Add Kudos
1
Bookmarks
Bookmark this Post
User avatar
Pratham_Patil24
Joined: 15 Jun 2024
Last visit: 24 Mar 2026
Posts: 30
Own Kudos:
Given Kudos: 504
GMAT Focus 1: 515 Q78 V76 DI72
GMAT Focus 2: 605 Q79 V82 DI79
Products:
GMAT Focus 2: 605 Q79 V82 DI79
Posts: 30
Kudos: 4
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Hi Marty,

Thanks for the detailed explanation!

Could you help understanstand why the probability that 0 units will be defective is 0.99 whole raised to 10?

Regards,
PP
MartyMurray
When a certain manufacturer produces a unit of its product, the probability that the unit will be defective is 0.01. If the manufacturer is to produce 10 units of its product, what is the probability that at least 1 of the 10 units produced will be defective?

The question asks for the probability that "at least 1" of the 10 units produced will be defective.

One way to answer such a question would be to determine the probability that 1 unit will be defective, the probability that 2 units will be defective, the probability that 3 units will be defective, and so on up to the probability that 10 units will be defective and add those probabilities to determine the total probability that at least 1 will be defective.

However, that method would take a lot of work, and there's a much more efficient way to calculate the probability that at least 1 will be defective.

We can simply find the probability that 0 units will be defective and subtract that probability from 1.

The reason that approach works is that the probability that 0 will be defective and the probabilities that 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 will be defective add to 1.

Since the probability that a given unit will be defective is 0.01, the probability that a given unit will not be defective is 0.99.

So, the probability that 0 units will be defective is \(0.99^{10}\).

Thus, the probability that at least 1 will be defective is \(1 - 0.99^{10}\).

A. \((0.01)^{10}\)

B. \((0.01)^9(0.99)\)

C. \((0.01)(0.99)^9\)

D. \(1-(0.01)^{10}\)

E. \(1-(0.99)^{10}\)


Correct answer: E
User avatar
esimon
Joined: 19 May 2024
Last visit: 10 May 2025
Posts: 2
Own Kudos:
1
 [1]
Given Kudos: 10
Posts: 2
Kudos: 1
 [1]
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
In this problem, we are given:

• The probability that a unit is defective, p = 0.01 .
• The number of units produced, n = 10 .
• We are asked to find the probability that at least one of the 10 units will be defective.

The probability of at least one defective unit can be found by calculating the complement of the probability that none of the units are defective.

1. Find the probability that none of the units are defective:
• The probability that a unit is not defective is 1 - p = 0.99 .
• For all 10 units to be non-defective, the probability is (0.99)^{10} .
2. Calculate the probability of at least one defective unit:

P(at least one defective) = 1 - P(no defective units)


= 1 - (0.99)^{10}


Answer:

The correct option is:
E. 1 - (0.99)^{10}
User avatar
Pratham_Patil24
Joined: 15 Jun 2024
Last visit: 24 Mar 2026
Posts: 30
Own Kudos:
Given Kudos: 504
GMAT Focus 1: 515 Q78 V76 DI72
GMAT Focus 2: 605 Q79 V82 DI79
Products:
GMAT Focus 2: 605 Q79 V82 DI79
Posts: 30
Kudos: 4
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Gotcha, thank you very much!
esimon
In this problem, we are given:

• The probability that a unit is defective, p = 0.01 .
• The number of units produced, n = 10 .
• We are asked to find the probability that at least one of the 10 units will be defective.

The probability of at least one defective unit can be found by calculating the complement of the probability that none of the units are defective.

1. Find the probability that none of the units are defective:
• The probability that a unit is not defective is 1 - p = 0.99 .
• For all 10 units to be non-defective, the probability is (0.99)^{10} .
2. Calculate the probability of at least one defective unit:

P(at least one defective) = 1 - P(no defective units)


= 1 - (0.99)^{10}


Answer:

The correct option is:
E. 1 - (0.99)^{10}
User avatar
bumpbot
User avatar
Non-Human User
Joined: 09 Sep 2013
Last visit: 04 Jan 2021
Posts: 38,957
Own Kudos:
Posts: 38,957
Kudos: 1,117
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Automated notice from GMAT Club BumpBot:

A member just gave Kudos to this thread, showing it’s still useful. I’ve bumped it to the top so more people can benefit. Feel free to add your own questions or solutions.

This post was generated automatically.
Moderators:
Math Expert
109776 posts
Tuck School Moderator
853 posts