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If a pencil is selected at random from a desk drawer, what

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If a pencil is selected at random from a desk drawer, what [#permalink]

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If a pencil is selected at random from a desk drawer, what is the probability that the pencil is red?

(1) There are 6 black and 4 orange pencils among the pencils in the drawer.
(2) There are three times as many red pencils in the drawer as pencils of all the other colors combined.
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Re: If a pencil is selected at random from a desk drawer, what [#permalink]

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If a pencil is selected at random from a desk drawer, what is the probability that the pencil is red?

(1) There are 6 black and 4 orange pencils among the pencils in the drawer. This one is clearly insufficient because we know nothing about red pencils.

(2) There are three times as many red pencils in the drawer as pencils of all the other colors combined. So, if there are x other color pencils, then there are 3x red pencils, so the probability of picking red is (red)/(total) = 3x/(x+3x) = 3/4. Sufficient.

Answer: B.
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Re: If a pencil is selected at random from a desk drawer, what [#permalink]

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Re: If a pencil is selected at random from a desk drawer, what [#permalink]

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New post 03 May 2016, 14:11
Bunuel wrote:
If a pencil is selected at random from a desk drawer, what is the probability that the pencil is red?

(1) There are 6 black and 4 orange pencils among the pencils in the drawer. This one is clearly insufficient because we know nothing about red pencils.

(2) There are three times as many red pencils in the drawer as pencils of all the other colors combined. So, if there are x other color pencils, then there are 3x red pencils, so the probability of picking red is (red)/(total) = 3x/(x+3x) = 3/4. Sufficient.

Answer: B.


Thank you Bunuel... great answer
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Re: If a pencil is selected at random from a desk drawer, what [#permalink]

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New post 08 Apr 2017, 02:39
Bunuel wrote:
If a pencil is selected at random from a desk drawer, what is the probability that the pencil is red?

(1) There are 6 black and 4 orange pencils among the pencils in the drawer. This one is clearly insufficient because we know nothing about red pencils.

(2) There are three times as many red pencils in the drawer as pencils of all the other colors combined. So, if there are x other color pencils, then there are 3x red pencils, so the probability of picking red is (red)/(total) = 3x/(x+3x) = 3/4. Sufficient.

Answer: B.


Hi Bunuel,

In the first choice isn't the probability of choosing the red pencil = 0 because there are no red pencils in the drawer.

Please clarify.
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Re: If a pencil is selected at random from a desk drawer, what [#permalink]

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gmatexam439 wrote:
Bunuel wrote:
If a pencil is selected at random from a desk drawer, what is the probability that the pencil is red?

(1) There are 6 black and 4 orange pencils among the pencils in the drawer. This one is clearly insufficient because we know nothing about red pencils.

(2) There are three times as many red pencils in the drawer as pencils of all the other colors combined. So, if there are x other color pencils, then there are 3x red pencils, so the probability of picking red is (red)/(total) = 3x/(x+3x) = 3/4. Sufficient.

Answer: B.


Hi Bunuel,

In the first choice isn't the probability of choosing the red pencil = 0 because there are no red pencils in the drawer.

Please clarify.


No.

(1) says that "There are 6 black and 4 orange pencils among the pencils in the drawer". There might be some other color pencils in the drawer apart from black and orange.
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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.


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Re: If a pencil is selected at random from a desk drawer, what [#permalink]

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New post 08 Apr 2017, 02:49
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gmatexam439 wrote:
Bunuel wrote:
If a pencil is selected at random from a desk drawer, what is the probability that the pencil is red?

(1) There are 6 black and 4 orange pencils among the pencils in the drawer. This one is clearly insufficient because we know nothing about red pencils.

(2) There are three times as many red pencils in the drawer as pencils of all the other colors combined. So, if there are x other color pencils, then there are 3x red pencils, so the probability of picking red is (red)/(total) = 3x/(x+3x) = 3/4. Sufficient.

Answer: B.


Hi Bunuel,

In the first choice isn't the probability of choosing the red pencil = 0 because there are no red pencils in the drawer.

Please clarify.


Hi gmatexam439,

No, the 1st statement doesn't imply that the number of red pencil = 0. Please read it carefully.

Quote:
There are 6 black and 4 orange pencils among the pencils in the drawer.


Notice the word among. The 1st statement implies there are more than two types of pencils in the drawer.

Hope it helps.
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Re: If a pencil is selected at random from a desk drawer, what [#permalink]

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New post 10 Apr 2017, 06:18
Bunuel wrote:
gmatexam439 wrote:
Bunuel wrote:
If a pencil is selected at random from a desk drawer, what is the probability that the pencil is red?

(1) There are 6 black and 4 orange pencils among the pencils in the drawer. This one is clearly insufficient because we know nothing about red pencils.

(2) There are three times as many red pencils in the drawer as pencils of all the other colors combined. So, if there are x other color pencils, then there are 3x red pencils, so the probability of picking red is (red)/(total) = 3x/(x+3x) = 3/4. Sufficient.

Answer: B.


Hi Bunuel,

In the first choice isn't the probability of choosing the red pencil = 0 because there are no red pencils in the drawer.

Please clarify.



No.

(1) says that "There are 6 black and 4 orange pencils among the pencils in the drawer". There might be some other color pencils in the drawer apart from black and orange.



Thank you Bunuel :)
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Re: If a pencil is selected at random from a desk drawer, what [#permalink]

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New post 10 Apr 2017, 06:19
ganand wrote:
gmatexam439 wrote:
Bunuel wrote:
If a pencil is selected at random from a desk drawer, what is the probability that the pencil is red?

(1) There are 6 black and 4 orange pencils among the pencils in the drawer. This one is clearly insufficient because we know nothing about red pencils.

(2) There are three times as many red pencils in the drawer as pencils of all the other colors combined. So, if there are x other color pencils, then there are 3x red pencils, so the probability of picking red is (red)/(total) = 3x/(x+3x) = 3/4. Sufficient.

Answer: B.


Hi Bunuel,

In the first choice isn't the probability of choosing the red pencil = 0 because there are no red pencils in the drawer.

Please clarify.


Hi gmatexam439,

No, the 1st statement doesn't imply that the number of red pencil = 0. Please read it carefully.

Quote:
There are 6 black and 4 orange pencils among the pencils in the drawer.


Notice the word among. The 1st statement implies there are more than two types of pencils in the drawer.

Hope it helps.


Thank you :)
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Helpful links:
1. Useful Formulae, Concepts and Tricks-Quant
2. e-GMAT's ALL SC Compilation
3. LSAT RC compilation
4. Actual LSAT CR collection by Broal
5. QOTD RC (Carcass)
6. Challange OG RC

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Re: If a pencil is selected at random from a desk drawer, what [#permalink]

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New post 10 Apr 2017, 08:30
If a pencil is selected at random from a desk drawer, what is the probability that the pencil is red?

(1) There are 6 black and 4 orange pencils among the pencils in the drawer.
No mention that red pencils are zero in number.
NS.
(2) There are three times as many red pencils in the drawer as pencils of all the other colors combined.

Suff. 3/4.

Ans B

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Re: If a pencil is selected at random from a desk drawer, what   [#permalink] 10 Apr 2017, 08:30
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