Source: Revised GRE PDF 1st Ed. Section 6: Math; #5 (p. 84)

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# The average (arithmetic mean) of 100 measurements is

The average (arithmetic mean) of 100 measurements is 23, and the average of 50 additional measurements is 27. Quantity A : The average of the 150 measurements Quantity B : 25 Quantity A is greater., Quantity B is greater., The two quantities are equal., The relationship cannot be determined from the information given.

### 2 Explanations

18

Alan Romero

[(23*100)+(27*50)] / 150 = 24.33

Nov 16, 2012 • Comment

Chris Lele, Magoosh Tutor

Hi Alan,
You want to be careful not to actually do the math on QC, unless you are uncertain of the intuitive approach. Doing the math takes time and can yield an incorrect answer.
Following the intuition that the average is going to "lean" towards 23, and therefore has to be less than 25 gets you the answer really quickly :).

Kalina Gajda

Hi Chris! Is the equation that Alan did correct?

Yes, the math is correct, but it is much better to use the intuitive approach here.

8 Chris Lele, Magoosh Tutor

Sep 26, 2012 • Comment