mimi0102 wrote:
What is the average (arithmetic mean) of the first 90 measurements in a certain list of 92 measurements?
(1) The average of 92 measurements is 7.0 centimeters.
(2) The average of the last 2 measurements is 7.2 centimeters.
You need the average of first 90 measurements.
(1) The average of 92 measurements is 7.0 centimeters.
We don't know what the last two measurements are so we cannot find the average of 90 measurements.
(2) The average of the last 2 measurements is 7.2 centimeters.
We don't know what the first 90 measurements are so we cannot find their average
Together we know that the average of all 92 measurements is 7 so sum of all measurements s 7*92.
We know that the average of last 2 is 7.2 so sum of last two is 7.2*2.
So we get the sum of first 90 measurements = 7*92 - 7.2*2
We can calculate this and divide by 90 to get the average. So both statements together are sufficient.
Answer (C)
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Karishma
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