Author 
Message 
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 46237

Question Stats:
75% (00:53) correct 25% (01:35) wrong based on 126 sessions
HideShow timer Statistics



Math Expert
Joined: 02 Sep 2009
Posts: 46237

Re M0531 [#permalink]
Show Tags
16 Sep 2014, 00:26
Official Solution:A flower shop has 2 tulips, 2 roses, 2 daisies, and 2 lilies. If two flowers are sold at random, what is the probability of not picking exactly two tulips? A. \(\frac{1}{8}\) B. \(\frac{1}{7}\) C. \(\frac{1}{2}\) D. \(\frac{7}{8}\) E. \(\frac{27}{28}\) The probability of not picking exactly two tulips is 1 minus the probability of picking 2 tulips. Out of 8 flowers, there is a 2 out of 8 chance of picking a tulip: \(\frac{2}{8} = \frac{1}{4}\). Out of the 7 remaining flowers, there is a 1 out of 7 or \(\frac{1}{7}\) chance of picking a tulip. Multiply the two fractions together to get the probability of picking both tulips: \(\frac{1}{4}*\frac{1}{7} = \frac{1}{28}\) Find probability of not picking exactly two tulips using the following equation: P (both not Tulips) = 1  P(both Tulips) \(1\frac{1}{28} = \frac{28}{28}\frac{1}{28} = \frac{27}{28}\) Answer: E
_________________
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? Extrahard Quant Tests with Brilliant Analytics



Intern
Joined: 03 Apr 2015
Posts: 10
Concentration: General Management, International Business

Re: M0531 [#permalink]
Show Tags
02 Oct 2015, 06:01
Hi Bunel, I thought : Probability of not picking two tulips : 6/8*5/7=5/12 I know I didn't get the correct answer but why do I have to find first the probability of getting both tulips (as you suggest)? Could you please explain me ? Thanks, Daniela
_________________
Daniela
From 330  Doing my best to beat the gmat!!



Math Expert
Joined: 02 Sep 2009
Posts: 46237

Re: M0531 [#permalink]
Show Tags
02 Oct 2015, 08:58



Intern
Joined: 03 Apr 2015
Posts: 10
Concentration: General Management, International Business

Re: M0531 [#permalink]
Show Tags
02 Oct 2015, 11:34
Thank you very much, Bunel. But why are you multiplying the probability of getting tulips (2/8) by 2? 2*2/8 (doesn't make sense in my head). :S Thanks
_________________
Daniela
From 330  Doing my best to beat the gmat!!



Intern
Joined: 06 May 2014
Posts: 6

Re: M0531 [#permalink]
Show Tags
02 Oct 2015, 23:34
dmatinho wrote: Thank you very much, Bunel.
But why are you multiplying the probability of getting tulips (2/8) by 2? 2*2/8 (doesn't make sense in my head). :S
Thanks 2 because order matters, first can be a tulip or second can be a tulip



Math Expert
Joined: 02 Sep 2009
Posts: 46237

Re: M0531 [#permalink]
Show Tags
03 Oct 2015, 05:04



Intern
Joined: 06 May 2014
Posts: 6

Re: M0531 [#permalink]
Show Tags
03 Oct 2015, 09:47
Bunuel wrote: Official Solution:
A flower shop has 2 tulips, 2 roses, 2 daisies, and 2 lilies. If two flowers are sold at random, what is the probability of not picking exactly two tulips?
A. \(\frac{1}{8}\) B. \(\frac{1}{7}\) C. \(\frac{1}{2}\) D. \(\frac{7}{8}\) E. \(\frac{27}{28}\)
The probability of not picking exactly two tulips is 1 minus the probability of picking 2 tulips. Out of 8 flowers, there is a 2 out of 8 chance of picking a tulip: \(\frac{2}{8} = \frac{1}{4}\). Out of the 7 remaining flowers, there is a 1 out of 7 or \(\frac{1}{7}\) chance of picking a tulip. Multiply the two fractions together to get the probability of picking both tulips: \(\frac{1}{4}*\frac{1}{7} = \frac{1}{28}\)
Find probability of not picking exactly two tulips using the following equation: P (both not Tulips) = 1  P(both Tulips) \(1\frac{1}{28} = \frac{28}{28}\frac{1}{28} = \frac{27}{28}\)
Answer: E Can this be solved by permutation/combination also? Total num of ways two tulips be selected/Total num of ways any two flowers be selected? And then you subtract that from 1? I would like to understand the explanation if anyone can provide please.



Intern
Joined: 25 Nov 2014
Posts: 3

Re: M0531 [#permalink]
Show Tags
20 Jul 2016, 06:55
2 tulips out of 8 flowers can be selected by 1 way.
Total No. of ways 2 flowers can be selected out of 8 flowers is 8c2= 7*8/2= 28
Probability of selecting 2 tulips out of 8 flowers is 1/28.
Therefor P(Not Selecting a Tulip)= 1(1/28)= 281/28=27/28



Intern
Joined: 23 Jan 2017
Posts: 2

Re: M0531 [#permalink]
Show Tags
19 Jan 2018, 12:03
Why wouldn't the answer be 1  (2/8) squared?
I got the answer correct, but I'm just trying to conceptualize why, if we are selling/picking two tulips simultaneously, why the chances of picking the second tulip would be reduced to (1/7).
Or am I just implicitly assuming that the tulips are sold one after the other?



Intern
Joined: 23 Jan 2017
Posts: 2

Re: M0531 [#permalink]
Show Tags
13 Feb 2018, 08:46
Bunuel wrote: gillm wrote: dmatinho wrote: Thank you very much, Bunel.
But why are you multiplying the probability of getting tulips (2/8) by 2? 2*2/8 (doesn't make sense in my head). :S
Thanks 2 because order matters, first can be a tulip or second can be a tulip ____________ Yes, that's right. Hi Bunuel, I am quoting you hoping that you will get a notification. Can you please help? > Why wouldn't the answer be 1  (2/8) squared? I got the answer correct, but I'm just trying to conceptualize why, if we are selling/picking two tulips simultaneously, why the chances of picking the second tulip would be reduced to (1/7). Or am I just implicitly assuming that the tulips are sold one after the other?



Math Expert
Joined: 02 Sep 2009
Posts: 46237

Re: M0531 [#permalink]
Show Tags
13 Feb 2018, 08:53










