BeepBoop wrote:
Bunuel wrote:
A certain list consists of 3 different numbers. Does the median of the 3 numbers equal the average (arithmetic mean) of the 3 numbers?
Say the three numbers are x, y, and x, where x < y < z. The median would be y and the average would be (x + y + z)/3. So, the question asks whether y = (x + y + z)/3, or whether 2y = x + z.
(1) The range of the 3 numbers is equal to twice the difference between the greatest number and the median --> the range is the difference between the largest and the smallest numbers of the set, so in our case z - x. We are given that z - x = 2(z - y) --> 2y = x + z. Sufficient.
(2) The sum of the 3 numbers is equal to 3 times one of the numbers --> the sum cannot be 3 times smallest numbers or 3 times largest number, thus x + y + z = 3y --> x + z = 2y. Sufficient.
Answer: D.
Hope it's clear.
Hi
Bunuel !
Thanks a lot for the explanation, it's concise and to the point - and these help a lot!
Could I ask one thing, though? In the second statement, you mention that the sum cannot be three times the smallest or largest number.
Why not? Is there a rule for series/sets that forbids this, or is this some logical deduction?
All the best,
Gil
We have that x < y < z.
The sum = x + y + z.
Obviously 3x < x + y + z < 3z because x < y < z (x + x + < x + y + z < z + z + z).
Does this make sense?[/quote]
Oh wow when you put it like that it does. Thanks a lot![/quote]
Hi, I tried some derivation- may be helpful thus posting it here:
For the 2nd statement, I tried solving and deriving- 3nos: a,b,c where a<b<c
Say 3 times the mean = 3 times smallest no. Thus
a+b+c=3a
Thus b+c=2a
This cannot be possible until b and c are less than or equal to a. But the qs states that these 3 numbers are distinct. Hence not possible. Same would be the case if the sum is 3 times the greatest number. a+b=2c... not possible because of the above mentioned reason