GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 22 Sep 2018, 02:18

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

The probability that event M will not occur is 0.8 and the probability

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 49300
The probability that event M will not occur is 0.8 and the probability  [#permalink]

Show Tags

New post 15 Jun 2016, 01:32
5
37
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

70% (00:57) correct 30% (01:10) wrong based on 1409 sessions

HideShow timer Statistics

The probability that event M will not occur is 0.8 and the probability that event R will not occur is 0.6. If events M and R cannot both occur, which of the following is the probability that either event M or event R will occur?

A) 1/5
B) 2/5
C) 3/5
D) 4/5
E) 12/25

_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Most Helpful Community Reply
Manager
Manager
avatar
Joined: 06 Jun 2014
Posts: 90
Location: United States
Concentration: Finance, General Management
GMAT 1: 450 Q27 V21
GPA: 3.47
GMAT ToolKit User
Re: The probability that event M will not occur is 0.8 and the probability  [#permalink]

Show Tags

New post 03 Jul 2016, 14:34
4
2
Just made a mistake by multiplying 0.2 and 0.4, got \(\frac{2}{25}\)

Note to self: "multiply" when there is an "AND", and "add" when there is an "OR"

we should be adding 0.2+0.4 = 0.6 or \(\frac{3}{5}\)
_________________

1) Kaplanprep 450 Q27 V21
2) Manhattan 530 Q35 V28
3) GmatPrep 450 Q33, V19
4) Veritas 460 Q31, V23
5) Veritas 440 Q 30, V21
6) Veritas 500 Q34, V 25
7) Gmat 420 Q27, V23
8) Veritas 520 Q36, V26 2/2
9) Veritas 540 Q37, V28 4/19
10)Manhattan 560 Q40, V28 4/28

General Discussion
Director
Director
User avatar
G
Joined: 20 Feb 2015
Posts: 733
Concentration: Strategy, General Management
Premium Member CAT Tests
The probability that event M will not occur is 0.8 and the probability  [#permalink]

Show Tags

New post Updated on: 15 Jun 2016, 04:31
p(m) =0.2
p(r) =0.4
p(m intersection r) = 0 (If events M and R cannot both occur)
p(m or r) = 0.2+0.4 =0.6

Corrected !!

Originally posted by CounterSniper on 15 Jun 2016, 03:52.
Last edited by CounterSniper on 15 Jun 2016, 04:31, edited 1 time in total.
Senior Manager
Senior Manager
User avatar
Joined: 18 Jan 2010
Posts: 254
Re: The probability that event M will not occur is 0.8 and the probability  [#permalink]

Show Tags

New post 15 Jun 2016, 04:04
1
4
Bunuel wrote:
The probability that event M will not occur is 0.8 and the probability that event R will not occur is 0.6. If events M and R cannot both occur, which of the following is the probability that either event M or event R will occur?

A) 1/5
B) 2/5
C) 3/5
D) 4/5
E) 12/25


P(R) = 1 - 0.8= 0.2
P(M) = 1 -0.6 = 0.4

Given that both events are mutually exclusive.

Prob that either event M or event R will occur = 0.2+0.4 = 0.6 = (6/10) = (3/5)

C is the answer.
Intern
Intern
avatar
Joined: 01 May 2015
Posts: 41
Re: The probability that event M will not occur is 0.8 and the probability  [#permalink]

Show Tags

New post 15 Jun 2016, 23:07
1
Got it wrong.

p(m) =0.2
p(r) =0.4

So, I calculated probability as sum of:

i) m occurs but r does not occur = 0.2*0.6
ii) r occurs but m does not occur = 0.4*0.8

So, probability = 0.2*0.6 + 0.4*0.8 = 0.44 = 11/25!
Intern
Intern
User avatar
B
Joined: 17 Jun 2016
Posts: 49
Re: The probability that event M will not occur is 0.8 and the probability  [#permalink]

Show Tags

New post 26 Sep 2016, 18:55
Can someone please explain why is it not
0.8*0.4+0.2*0.6
11/25
:?
Manager
Manager
avatar
S
Joined: 13 Apr 2010
Posts: 90
Reviews Badge
Re: The probability that event M will not occur is 0.8 and the probability  [#permalink]

Show Tags

New post 10 Oct 2016, 00:53
2
3
shonakshi wrote:
Can someone please explain why is it not
0.8*0.4+0.2*0.6
11/25
:?



I think , you are trying to calculate probability by multiplying P(M)*P(~R) + P(R)*P(~M) . This is wrong .
Formula is P(M or R) = P(M) + P(R) - P (M and R) => 0.2 + 0.4 - 0 = > 0.6 or 3/5 (Answer is C) .
Board of Directors
User avatar
P
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4032
Location: India
GPA: 3.5
WE: Business Development (Commercial Banking)
GMAT ToolKit User Premium Member
The probability that event M will not occur is 0.8 and the probability  [#permalink]

Show Tags

New post 10 Oct 2016, 07:58
1
2
shonakshi wrote:
Can someone please explain why is it not
0.8*0.4+0.2*0.6
11/25
:?


Go through this page, it will answer all your queries...

https://people.richland.edu/james/lectu ... 5-rul.html

Hope that helps..
_________________

Thanks and Regards

Abhishek....

PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS

How to use Search Function in GMAT Club | Rules for Posting in QA forum | Writing Mathematical Formulas |Rules for Posting in VA forum | Request Expert's Reply ( VA Forum Only )

Target Test Prep Representative
User avatar
G
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 3515
Location: United States (CA)
The probability that event M will not occur is 0.8 and the probability  [#permalink]

Show Tags

New post 11 Oct 2016, 16:59
2
1
Bunuel wrote:
The probability that event M will not occur is 0.8 and the probability that event R will not occur is 0.6. If events M and R cannot both occur, which of the following is the probability that either event M or event R will occur?

A) 1/5
B) 2/5
C) 3/5
D) 4/5
E) 12/25


We are given that the probability that event M will not occur is 0.8 and the probability that event R will not occur is 0.6 and that events M and R cannot both occur.

We need to determine the probability that either event M or event R will occur.

The probability that event M will occur is 1 - 0.8 = 0.2 = 1/5

The probability that event R will occur is 1 - 0.6 = 0.4 = 2/5

Since events M and R cannot both occur , the probability that either event M or event R will occur is 1/5 + 2/5 =3/5.

Answer: C
_________________

Scott Woodbury-Stewart
Founder and CEO

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Intern
Intern
avatar
Joined: 14 Jul 2016
Posts: 5
Re: The probability that event M will not occur is 0.8 and the probability  [#permalink]

Show Tags

New post 13 Oct 2016, 05:01
ScottTargetTestPrep wrote:
Bunuel wrote:
The probability that event M will not occur is 0.8 and the probability that event R will not occur is 0.6. If events M and R cannot both occur, which of the following is the probability that either event M or event R will occur?

A) 1/5
B) 2/5
C) 3/5
D) 4/5
E) 12/25


We are given that the probability that event M will not occur is 0.8 and the probability that event R will not occur is 0.6 and that events M and R cannot both occur.

We need to determine the probability that either event M or event R will occur.

The probability that event M will occur is 1 - 0.8 = 0.2 = 1/5

The probability that event R will occur is 1 - 0.6 = 0.4 = 2/5

Since events M and R cannot both occur , the probability that either event M or event R will occur is 1/5 + 2/5 =3/5.

Answer: C




We should take into consideration that both cannot occurs. please explain
Board of Directors
User avatar
P
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4032
Location: India
GPA: 3.5
WE: Business Development (Commercial Banking)
GMAT ToolKit User Premium Member
Re: The probability that event M will not occur is 0.8 and the probability  [#permalink]

Show Tags

New post 13 Oct 2016, 07:44
1
1
Bunuel wrote:
The probability that event M will not occur is 0.8 and the probability that event R will not occur is 0.6.If events M and R cannot both occur, which of the following is the probability that either event M or event R will occur?

A) 1/5
B) 2/5
C) 3/5
D) 4/5
E) 12/25


M' = 0.80 So M = 0.20
R' = 0.60 So R = 0.40
Quote:
probability that either event M or event R will occur?

M+R = M + R - MR
Quote:
events M and R cannot both occur

So , MR = 0

M+R = 0.20 + 0.40 - 0

Or, M+R = 0.60

Hence answer will be 0.60 or (C) 3/5

SOHAM6185 wrote:
We should take into consideration that both cannot occurs. please explain


The reason is highlighted...

Try to solve this question using VENN Diagram approach it will be crystal clear...
_________________

Thanks and Regards

Abhishek....

PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS

How to use Search Function in GMAT Club | Rules for Posting in QA forum | Writing Mathematical Formulas |Rules for Posting in VA forum | Request Expert's Reply ( VA Forum Only )

Senior Manager
Senior Manager
avatar
S
Joined: 29 Jun 2017
Posts: 418
Re: The probability that event M will not occur is 0.8 and the probability  [#permalink]

Show Tags

New post 30 Jun 2017, 03:45
sb0541 wrote:
shonakshi wrote:
Can someone please explain why is it not
0.8*0.4+0.2*0.6
11/25
:?



I think , you are trying to calculate probability by multiplying P(M)*P(~R) + P(R)*P(~M) . This is wrong .
Formula is P(M or R) = P(M) + P(R) - P (M and R) => 0.2 + 0.4 - 0 = > 0.6 or 3/5 (Answer is C) .


yes, that is why p(m and n) need to be zero.
Manager
Manager
avatar
S
Joined: 08 Apr 2017
Posts: 83
Re: The probability that event M will not occur is 0.8 and the probability  [#permalink]

Show Tags

New post 08 Nov 2017, 17:00
shonakshi wrote:
Can someone please explain why is it not
0.8*0.4+0.2*0.6
11/25
:?


The probability that event M will not occur is 0.8 and the probability that event R will not occur is 0.6. If events M and R cannot both occur, which of the following is the probability that either event M or event R will occur?

Let's break this down

M will not occur = 0.8; M will occur = 0.2
R will not occur = 0.6; R will occur = 0.4

P(M or R) = P(M) + P(R) - P (M and R)
P(M or R) = 0.2 + 0.4 - 0
P(M or R) = 0.6 = 6/10 = 3/5

Note: Multiplying occurrence that will not occur + Multiplying occurrence that will occur is not equal to either event M or event R will occur
Manager
Manager
avatar
B
Joined: 29 Nov 2016
Posts: 53
Re: The probability that event M will not occur is 0.8 and the probability  [#permalink]

Show Tags

New post 11 Mar 2018, 20:57
shonakshi wrote:
Can someone please explain why is it not
0.8*0.4+0.2*0.6
11/25
:?

Once you say that event M and event R can not occur together , it means that both are mutually exclusive.
P(M).P(R)=0

Posted from my mobile device

Posted from my mobile device
Senior Manager
Senior Manager
avatar
S
Joined: 29 Jun 2017
Posts: 418
Re: The probability that event M will not occur is 0.8 and the probability  [#permalink]

Show Tags

New post 14 Mar 2018, 08:18
be careful
there are 2 cases
case 1
1= p (a happen)+ p (b happen)- p (both a and b happen) +p (neither a nor b happen) . this is ven digram

case 2
1= p (a dose not happen)+ p(b dose not happen)- p (neither a nor b happen)+ p (both a and b happen). this is ven diagram
p ( only a happen) is in p (b dose not happen).

so, there is two scenario here.
Intern
Intern
avatar
Joined: 24 Aug 2018
Posts: 1
Re: The probability that event M will not occur is 0.8 and the probability  [#permalink]

Show Tags

New post 24 Aug 2018, 08:07
GMATSkilled wrote:
shonakshi wrote:
Can someone please explain why is it not
0.8*0.4+0.2*0.6
11/25
:?


The probability that event M will not occur is 0.8 and the probability that event R will not occur is 0.6. If events M and R cannot both occur, which of the following is the probability that either event M or event R will occur?

Let's break this down

M will not occur = 0.8; M will occur = 0.2
R will not occur = 0.6; R will occur = 0.4

P(M or R) = P(M) + P(R) - P (M and R)
P(M or R) = 0.2 + 0.4 - 0
P(M or R) = 0.6 = 6/10 = 3/5

Note: Multiplying occurrence that will not occur + Multiplying occurrence that will occur is not equal to either event M or event R will occur


How can that formula be correct? What if the problem had said the probability that M will not occur is .5, and the probability that R will not occur is .5. Then according to your formula, you'd have:
P(M or R) = P(M) + P(R) - P(M and R)
P(M or R) = .5 + .5 - 0
P(M or R) = 1

So if two mutually exclusive events each have a 1/2 probability of occurring, then the probability of at least one of them occurring is 1 (100% of the time?) That doesn't make any sense to me, so I'm not exactly sure why that formula is what you're supposed to apply.

In a real-life scenario, that's like saying the Cardinals have a 40% chance to win the World Series, and the Yankees have a 20% chance to win, so the chance that one of them wins is 60% (since both of them cannot win)... Which doesn't make any sense. Again, what if you said the cardinals have an 80% chance to win and the Yankees have a 30% chance to win. So the chance that one of them wins is 110%?

The language in the question doesn't seem to suggest that either M or N must occur... In order to interpret the question the way the answer seems to, I would think the language would have to say something like "Out of 100 trials, M did not occur 80% of the time and N did not occur 60% of the time; if N and M never occurred on the same trial, what's the probability that a randomly selected trial will have M OR N occurring?" In that case, when you already have a list of events that happened, you could apply the formula P(M or R) = P(M) + P(R) - P(M and R)... Take it back to the 50% example, if you know that M occurred 50% of the time and N occurred 50% of the time, and M and N cannot happen, then you know that at least M or N had to happen every time. But when you're talking about the probability of a future event, as the problem seems to suggest, it doesn't make sense to just add the probabilities.

Can someone tell me if/how my reasoning is incorrect?
Intern
Intern
avatar
Joined: 12 Sep 2018
Posts: 1
Re: The probability that event M will not occur is 0.8 and the probability  [#permalink]

Show Tags

New post 14 Sep 2018, 18:49
Can someone please address the above challenge to this question's answer? I also disagree with the application of the formula used in the solution. This question is posing a future probability event.

What if the question was modified to probability of M occurring=90% and R occurring=90%? (So not occurring for either event is 10%). M and R are still mutually exclusive events.

If we apply the recommended formula P(M or R)=P(M) + P(R) -P(M and R), we get .9+.9-0=1.8. Wait, 1.8!? That doesn't even make sense.
Re: The probability that event M will not occur is 0.8 and the probability &nbs [#permalink] 14 Sep 2018, 18:49
Display posts from previous: Sort by

The probability that event M will not occur is 0.8 and the probability

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  

Events & Promotions

PREV
NEXT


GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.