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MHIKER
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A researcher was noting down a few values for his research 17 Nov 2020, 12:19
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B
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25% (medium)

Question Stats:

77% (01:34) correct 23% (01:55) wrong based on 84 sessions

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A researcher was noting down a few values for his research. He mistakenly wrote 42 instead of 24, because of which the average increased by 2. What was the number of values?
A. 8
B. 9
C. 13
D. 15
E. 17
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B
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A researcher was noting down a few values for his research 17 Nov 2020, 13:40
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MHIKER
A researcher was noting down a few values for his research. He mistakenly wrote 42 instead of 24, because of which the average increased by 2. What was the number of values?
A. 8
B. 9
C. 13
D. 15
E. 17
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42 instead of 24 increases the total by 42-24 = 18. The average increased by 2 when we increased the sum by 18, so we have \(\frac{18}{# of Values} = 2\). Then there are 9 values.

Ans: B
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A researcher was noting down a few values for his research 17 Nov 2020, 15:52
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When the researcher changed the number from 24 to 42, the increase in the average is +2

This means that 42 - 24 = 18 difference was spread out throughout the number of values to increase each number by 2.

18/9 = 2

Spreading out 18 among 9 numbers gives us a +2 increase.

Answer: B
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A researcher was noting down a few values for his research Updated on: 21 Nov 2020, 01:43
Originally posted by CrackverbalGMAT on 17 Nov 2020, 20:01.
Last edited by CrackverbalGMAT on 21 Nov 2020, 01:43, edited 1 time in total.
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Since Average = Sum of observations / # of observations, therefore Sum of observations = Average * # of observations.

Let the number of observations = n and let the average of the original data = x

Sum of observations of the original data = nx

The wrong observation is 42 and the correct observation is 24. The new sum of observations = nx - 42 + 24

The new average = x - 2. n remains the same.

Therefore \(\frac{nx - 42 + 24}{n} = x - 2\)

nx - 18 = nx - 2n

2n = 18

n = 9



Option B

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A researcher was noting down a few values for his research 21 Nov 2020, 00:24
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CrackVerbalGMAT
Since Average = Sum of observations / # of observations, therefore Sum of observations = Average * # of observations.

Let the number of observations = n and let the average of the original data = x

Sum of observations of the original data = nx

The wrong observation is 24 and the correct observation is 42. The new sum of observations = nx - 24 + 42

The new average = x + 2. n remains the same.

Therefore \(\frac{nx - 24 + 42}{n} = x + 2\)

nx - 18 = nx + 2n

2n = 18

n = 9

Option B

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Hi CrackVerbalGMAT

In the question, it is mentioned that "He mistakenly wrote 42 instead of 24". So 24 is the correct value and 42 is the wrong value, right?

In that case, it would be nx-42+24 = nx-18

Please correct me if i'm wrong
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A researcher was noting down a few values for his research 21 Nov 2020, 01:49
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shameeh
In the question, it is mentioned that "He mistakenly wrote 42 instead of 24". So 24 is the correct value and 42 is the wrong value, right?

In that case, it would be nx-42+24 = nx-18

Please correct me if i'm wrong
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Hi shameesh. Thanks for pointing it out. edited and corrected.
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A researcher was noting down a few values for his research 20 Dec 2020, 08:53
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MHIKER
A researcher was noting down a few values for his research. He mistakenly wrote 42 instead of 24, because of which the average increased by 2. What was the number of values?
A. 8
B. 9
C. 13
D. 15
E. 17
Show more

Let, \(n\) is the total number of values.

\(Average*number \ of \ values = Total\)

So, \(2n=42-24=18\)

\(n=9\)

The answer is \(B\)
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A researcher was noting down a few values for his research 20 Dec 2020, 19:33
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MHIKER
A researcher was noting down a few values for his research. He mistakenly wrote 42 instead of 24, because of which the average increased by 2. What was the number of values?
A. 8
B. 9
C. 13
D. 15
E. 17
Show more

If you want to solve the PS as an increase with the total value for the mistake then the following may be an option:

The increase of value for the mistake \(= 42-24=18\)
\(N=\)Total value

\(x=\) First average

So, \(\frac{nx+18}{n}=x+2\)

\(=nx+18=nx+2n\)

\(=2n=18\)

\(n=9\)

I was looking for this kind of understanding.
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