chetan2u
Was the median height of the 25 children in a certain class at least 2 percent greater than the average (arithmetic mean) height of the 25 children?
Is median height\(\geq \) 102 % of Average height.
(1) The median height of the 25 children was 2 centimeters greater than their average height.
Median height =Average height+2
If Average height is 100cm or less, 2cm will be at least 2% of the average height. Answer is YES
If Average height >100cm, answer is NO.
Insufficient
(2) The sum of the heights of the 25 children was less than 2,550 centimeters
So Average \(\leq \frac{2550}{25}\) or 102cm.
Nothing about Median height.
Insufficient
Combined
If average height is 100 or less, answer is yes.
If Average height is between 100 and 102, answer is No.
insufficient
E
I want to know what I am doing incorrectly in my approach:
question is asking if the median is at least 2% greater than the average, which in equation is:
(median/average) - 1 >= 0.02
(1) states median is 2 cm greater than the average height, hence median = average + 2
substituting this into the equation above, i get: (average + 2)/(average) - 1 >= 0.02
simplify:
(average)/(average) + (2)/(average) - 1 >= 0.02
1 + (2/average) - 1 >= 0.02
2/average >= 0.02
2/0.02 >= average
average <= 100
given average is less than or equal to 100, at its max value:
average = 100, median = 102 -> median is at least 2% greater than average
if average is any value below 100, median is larger by more than 2%:
i.e. if average = 50, median = 52
52/50 -1 = 0.04 or 4%
by this logic, wouldn't (1) be sufficient to answer the question?
From (1) we do not get that \(0 < average \leq 100\). When you substitute