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What is the standard deviation of the values of the 20 coins in a

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Skywalker18
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What is the standard deviation of the values of the 20 coins in a [#permalink] New post   20 Jun 2016, 11:09
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What is the standard deviation of the values of the 20 coins in a certain jar ?

(1) The average (arithmetic mean ) value of the coins in the jar is 25 cents .

(2) All 20 coins in the jar have the same value .
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Divyadisha
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Re: What is the standard deviation of the values of the 20 coins in a [#permalink] New post   21 Jun 2016, 10:57
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Skywalker18 wrote:
What is the standard deviation of the values of the 20 coins in a certain jar ?

1. The average (arithmetic mean ) value of the coins in the jar is 25 cents .

2. All 20 coins in the jar have the same value .



1. The average (arithmetic mean ) value of the coins in the jar is 25 cents . We don't know other values to find out standard deviation. Not Sufficient.

2. All 20 coins in the jar have the same value . All the values are same means SD is 0. Sufficient

B is the answer
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Re: What is the standard deviation of the values of the 20 coins in a [#permalink] New post   19 Jan 2018, 09:00
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Skywalker18 wrote:
What is the standard deviation of the values of the 20 coins in a certain jar ?

1. The average (arithmetic mean ) value of the coins in the jar is 25 cents .

2. All 20 coins in the jar have the same value .



Target question: What is the standard deviation of the values of the 20 coins in a certain jar ?

Statement 1: The average (arithmetic mean ) value of the coins in the jar is 25 cents .
There are several cases that satisfy statement 1. Here are two:
Case a: All 20 coins are quarters (each is worth $0.25). This meets this condition that the average value is 25 cents. In this case, the standard deviation EQUALS 0
Case b: The 20 coins are NOT all quarters. In this case, the standard deviation does NOT equal 0
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: All 20 coins in the jar have the same value
The means the standard deviation EQUALS 0
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer: B

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Re: What is the standard deviation of the values of the 20 coins in a [#permalink] New post   18 Dec 2018, 22:24
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Standard deviation of a set of numbers is a non-negative quantity which equals (maximum number – minimum number) in the set.
Statement 1: We are given the mean of the set of numbers. We can’t find the maximum and the minimum number from this information .Hence, Insufficient.
Statement 2: It is given that all 20 coins in the jar have the same value. This means the S.D = 0.
Hence, Sufficient.
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Re: What is the standard deviation of the values of the 20 coins in a [#permalink] New post   27 Dec 2023, 21:10
what combinations of 20 coins equals an average of 25 without all being quarters? Seems like thats impossible to me and the answer is D.

Also do half dollars and dollar coins exist on the GMAT? Taking it sunday, would like to know before, but it probably wont come up anyways
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Re: What is the standard deviation of the values of the 20 coins in a [#permalink] New post   27 Dec 2023, 23:54
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ayooohelp wrote:
what combinations of 20 coins equals an average of 25 without all being quarters? Seems like thats impossible to me and the answer is D.

Also do half dollars and dollar coins exist on the GMAT? Taking it sunday, would like to know before, but it probably wont come up anyways


Circulating coins exist in denominations of 1¢, 5¢, 10¢, 25¢, 50¢, and $1.00. So, there are several combinations possible to average 25¢. For example, five 5¢ and fifteen 25¢ coins would average 20 cents.
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Re: What is the standard deviation of the values of the 20 coins in a [#permalink]
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