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14 Jan 2021, 08:25
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Difficulty:
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Question Stats:
86% (01:20) correct
14%
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wrong
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If there are 30 red and blue marbles in a jar, and the ratio of red to blue marbles is 2:3, what is the probability that, drawing twice, you will select two red marbles if you return the marbles after each draw?
A. 1/25
B. 2/25
C. 3/25
D. 4/25
E. 21/25
A. 1/25
B. 2/25
C. 3/25
D. 4/25
E. 21/25
XSatishX
Joined: 05 Jul 2020
Last visit: 17 Nov 2022
Posts: 100
Given Kudos: 36
Location: India
Concentration: Leadership, General Management
Schools: LBS '24 (D) ISB '23 (II) Tepper '24 (S)
GMAT 1: 650 Q49 V30
GMAT 2: 730 Q48 V41 (Online)
GPA: 3.8
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14 Jan 2021, 08:43
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We don't need the total number of marbles here as we have the ratio of red to blue marbles in the jar.
So the probability of picking a red marble = 2/5
As per the question, we are returning the marbles so every time we pick a marble the bag will have 30 marbles in the same ratio.
So the probability of picking two red marbles = 2/5*2/5 = 4/25
Not sure why this answer choice is missing here. If we are not returning these marbles than the probability will be 12/30*11/29 = 22/145.
So the probability of picking a red marble = 2/5
As per the question, we are returning the marbles so every time we pick a marble the bag will have 30 marbles in the same ratio.
So the probability of picking two red marbles = 2/5*2/5 = 4/25
Not sure why this answer choice is missing here. If we are not returning these marbles than the probability will be 12/30*11/29 = 22/145.
19 Jan 2021, 09:11
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Bunuel
Ratio of Red to Blue = 2:3 We have total 30
Hence \(5x=30, x= 6\)
Since we have 12 red marbles
Probability of picking 2 red marbles
\(\frac{12}{30}*\frac{12}{30}\)= \(\frac{144}{900}\)=\(\frac{4}{25}\)
Bunuel please look into this.
Ans should be \(\frac{4}{25}\)
