Last visit was: 25 Apr 2026, 15:11 It is currently 25 Apr 2026, 15:11
Home
Messages
Tests
Schools
Events
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.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel
User avatar
Konstantin Lynov
User avatar
Joined: 24 Jun 2003
Last visit: 19 Sep 2004
Posts: 71
Own Kudos:
14
Location: Moscow
Posts: 71
Kudos: 14
1) Two anti-aircraft guns are firing at 4 planes. P (they 08 Aug 2003, 02:58
Kudos
Add Kudos
Bookmarks
Bookmark this Post
1) Two anti-aircraft guns are firing at 4 planes. P (they are firing at the same plane)?
2) Three anti-aircraft guns are firing at 4 planes. P (they are firing at the same plane)?



Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Quantitative Questions Forum
Still interested in this question? Check out the "Best Topics" block below for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
avatar
stolyar
avatar
Joined: 03 Feb 2003
Last visit: 06 May 2014
Posts: 1,012
Own Kudos:
1,884
Posts: 1,012
Kudos: 1,884
1) Two anti-aircraft guns are firing at 4 planes. P (they 08 Aug 2003, 03:43
Kudos
Add Kudos
Bookmarks
Bookmark this Post
(1) 1*1/4=1/4

(2) 1*1/4*1/4=1/16
User avatar
Konstantin Lynov
User avatar
Joined: 24 Jun 2003
Last visit: 19 Sep 2004
Posts: 71
Own Kudos:
14
Location: Moscow
Posts: 71
Kudos: 14
1) Two anti-aircraft guns are firing at 4 planes. P (they 08 Aug 2003, 11:47
Kudos
Add Kudos
Bookmarks
Bookmark this Post
May I... explain? pls see previous message
avatar
stolyar
avatar
Joined: 03 Feb 2003
Last visit: 06 May 2014
Posts: 1,012
Own Kudos:
1,884
Posts: 1,012
Kudos: 1,884
1) Two anti-aircraft guns are firing at 4 planes. P (they 08 Aug 2003, 12:04
Kudos
Add Kudos
Bookmarks
Bookmark this Post
sure you may
your explanations are welcome
User avatar
MBA04
User avatar
Joined: 03 Jun 2003
Last visit: 06 Oct 2003
Posts: 51
Own Kudos:
4
Location: Uruguay
Posts: 51
Kudos: 4
1) Two anti-aircraft guns are firing at 4 planes. P (they 12 Aug 2003, 06:39
Kudos
Add Kudos
Bookmarks
Bookmark this Post
1) 1/4 * 1/4 *4 = 1/4
2) 1/4*1/4*1/4*4 = 1/16

Each anti air craft has 1/4 prob to be shooting at one plane, so 1/4*1/4 (two anti air craft). Then we multiply by 4 because we have 4 planes to choose
User avatar
p_malh
User avatar
Joined: 20 Aug 2003
Last visit: 23 Apr 2004
Posts: 34
Own Kudos:
1
Location: USA
Posts: 34
Kudos: 1
1) Two anti-aircraft guns are firing at 4 planes. P (they 25 Aug 2003, 03:55
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Quote:
1) 1/4 * 1/4 *4 = 1/4
2) 1/4*1/4*1/4*4 = 1/16

Each anti air craft has 1/4 prob to be shooting at one plane, so 1/4*1/4 (two anti air craft). Then we multiply by 4 because we have 4 planes to choose
Show more



Mbao4,

Shouldn't the first one be multiplied by 6 instead of 4, since we have 4C2 ways to choose 2 planes out of 4?

Please explain
User avatar
Konstantin Lynov
User avatar
Joined: 24 Jun 2003
Last visit: 19 Sep 2004
Posts: 71
Own Kudos:
14
Location: Moscow
Posts: 71
Kudos: 14
1) Two anti-aircraft guns are firing at 4 planes. P (they 27 Aug 2003, 12:12
Kudos
Add Kudos
Bookmarks
Bookmark this Post
p_malh
Quote:
1) 1/4 * 1/4 *4 = 1/4
2) 1/4*1/4*1/4*4 = 1/16

Each anti air craft has 1/4 prob to be shooting at one plane, so 1/4*1/4 (two anti air craft). Then we multiply by 4 because we have 4 planes to choose


Mbao4,

Shouldn't the first one be multiplied by 6 instead of 4, since we have 4C2 ways to choose 2 planes out of 4?

Please explain
Show more


Before Mba answers, let me try.

Think about two planes separately: the probability that one is firing is 100% or 1 (appears from the question stem). Now, the P that the second gun is firing at the same plane as the first one is 1/4, is't it? - four planes - one gun - this should be clear.

Multiply to get the total P. 1*1/4=1/4
Gabish?



Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Quantitative Questions Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!