Summer is Coming! Join the Game of Timers Competition to Win Epic Prizes. Registration is Open. Game starts Mon July 1st.

It is currently 18 Jul 2019, 23:32

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

A flower arrangement consists of 30 roses, each of which is either whi

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

Hide Tags

Find Similar Topics 
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 56265
A flower arrangement consists of 30 roses, each of which is either whi  [#permalink]

Show Tags

New post 04 Jul 2018, 00:08
00:00
A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

87% (00:55) correct 13% (01:00) wrong based on 122 sessions

HideShow timer Statistics


A flower arrangement consists of 30 roses, each of which is either white or red. If a rose is to be selected at random from the flower arrangement, the probability that the rose selected will be white is twice the probability that it will be red. How many white roses are in the flower arrangement?

A. 5
B. 10
C. 15
D. 20
E. 25

_________________
Senior Manager
Senior Manager
User avatar
G
Joined: 21 Jan 2015
Posts: 459
Location: India
Concentration: Strategy, Marketing
GMAT 1: 620 Q48 V28
GMAT 2: 690 Q49 V35
WE: Sales (Consumer Products)
GMAT ToolKit User Reviews Badge
Re: A flower arrangement consists of 30 roses, each of which is either whi  [#permalink]

Show Tags

New post 04 Jul 2018, 00:14
Ans: D
given that total roses =30
P(w)=2P(r)
We know there are only white or red roses so P(w)+P(r)=1
so 3P(r)=1 ; P(r) =1/3 this mean P(w) = 2/3 = 20/30 where 30 is the total outcome and 20 will be the favourable outcomes.
no. of white roses = 20

Bunuel wrote:
A flower arrangement consists of 30 roses, each of which is either white or red. If a rose is to be selected at random from the flower arrangement, the probability that the rose selected will be white is twice the probability that it will be red. How many white roses are in the flower arrangement?

A. 5
B. 10
C. 15
D. 20
E. 25

_________________
--------------------------------------------------------------------
The Mind is Everything, What we Think we Become.
e-GMAT Representative
User avatar
V
Joined: 04 Jan 2015
Posts: 2943
Re: A flower arrangement consists of 30 roses, each of which is either whi  [#permalink]

Show Tags

New post 05 Jul 2018, 04:01
3

Solution



Given:
    • Total number of roses in the flower arrangement = 30
    • Each rose is either white or red in color
    • A rose is randomly selected from the arrangement
    • The probability that the selected rose will be white = 2 * the probability that the selected rose will be red

To find:
    • Number of white roses in the arrangement

Approach and Working:
    • Assume the probability of the selected rose will be white as P(w), and the probability of the selected rose will be red as P(r)
    • P(r) + P(w) = 1, and ……………………………………. (1)
    • Also given, P(w) = 2 * P(r) …………………………... (2)
    • From (1) and (2), we get
      o P(r) = \(\frac{1}{3}\) and P(w) = \(\frac{2}{3}\)
    • P(w) = total number of WHITE roses/ total number of roses
    • Therefore, the number of white roses in the arrangement = \(\frac{2}{3} *\) total number of roses
    • Thus, number of white roses = \(\frac{2}{3} * 30\) = 20

Hence, the correct answer is option D.

Answer: D
_________________
Intern
Intern
User avatar
B
Joined: 17 May 2018
Posts: 49
Re: A flower arrangement consists of 30 roses, each of which is either whi  [#permalink]

Show Tags

New post 11 Jul 2018, 08:53
For the probability of having a white rose to be twice the probability of picking a red one, we need twice as many white roses as red, or 2 parts of white roses for each part of red roses.

To meet this ratio 2:1 in a total of 30 roses we need 20 white roses and 10 red.

Answer D
_________________
¿Tienes que presentar el GMAT y no sabes por dónde empezar?
¡Visita GMAT para Principiantes y recibe el curso completo gratis!
Intern
Intern
User avatar
B
Joined: 06 Oct 2017
Posts: 48
Location: Canada
GPA: 3.6
A flower arrangement consists of 30 roses, each of which is either whi  [#permalink]

Show Tags

New post 20 Jul 2018, 13:46
EgmatQuantExpert wrote:

Solution



Given:
    • Total number of roses in the flower arrangement = 30
    • Each rose is either white or red in color
    • A rose is randomly selected from the arrangement
    • The probability that the selected rose will be white = 2 * the probability that the selected rose will be red

To find:
    • Number of white roses in the arrangement

Approach and Working:
    • Assume the probability of the selected rose will be white as P(w), and the probability of the selected rose will be red as P(r)
    • P(r) + P(w) = 1, and ……………………………………. (1)
    • Also given, P(w) = 2 * P(r) …………………………... (2)
    • From (1) and (2), we get
      o P(r) = \(\frac{1}{3}\) and P(w) = \(\frac{2}{3}\)

    • P(w) = total number of WHITE roses/ total number of roses
    • Therefore, the number of white roses in the arrangement = \(\frac{2}{3} *\) total number of roses
    • Thus, number of white roses = \(\frac{2}{3} * 30\) = 20

Hence, the correct answer is option D.

Answer: D


I get up to the point where the 1/3 and 2/3 come in... am I missing something obvious? Because that makes zero sense to me and it is driving me crazy trying to figure it out. Where did the 1/3 come in?
Intern
Intern
avatar
B
Joined: 11 Jul 2018
Posts: 13
Re: A flower arrangement consists of 30 roses, each of which is either whi  [#permalink]

Show Tags

New post 20 Jul 2018, 14:20
1
aanjumz92 wrote:
EgmatQuantExpert wrote:

Solution



Given:
    • Total number of roses in the flower arrangement = 30
    • Each rose is either white or red in color
    • A rose is randomly selected from the arrangement
    • The probability that the selected rose will be white = 2 * the probability that the selected rose will be red

To find:
    • Number of white roses in the arrangement

Approach and Working:
    • Assume the probability of the selected rose will be white as P(w), and the probability of the selected rose will be red as P(r)
    • P(r) + P(w) = 1, and ……………………………………. (1)
    • Also given, P(w) = 2 * P(r) …………………………... (2)
    • From (1) and (2), we get
      o P(r) = \(\frac{1}{3}\) and P(w) = \(\frac{2}{3}\)

    • P(w) = total number of WHITE roses/ total number of roses
    • Therefore, the number of white roses in the arrangement = \(\frac{2}{3} *\) total number of roses
    • Thus, number of white roses = \(\frac{2}{3} * 30\) = 20

Hence, the correct answer is option D.

Answer: D


I get up to the point where the 1/3 and 2/3 come in... am I missing something obvious? Because that makes zero sense to me and it is driving me crazy trying to figure it out. Where did the 1/3 come in?
Consider the whole question more simply, this is a simple case of probability so the probability will be directly proportional to the number of items (that is flowers here).
So when they say that the probability of getting white is double than that of getting red, it simply means that is x is the number of red flowers, then 2x is the number of white flowers in the setup.
After this,
x+2x=30
x=10
Therefore number of white flowers is 2x ie 20

Sent from my Redmi Note 3 using GMAT Club Forum mobile app
GMAT Club Bot
Re: A flower arrangement consists of 30 roses, each of which is either whi   [#permalink] 20 Jul 2018, 14:20
Display posts from previous: Sort by

A flower arrangement consists of 30 roses, each of which is either whi

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





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