BTGmoderatorDC wrote: ↑Wed Dec 11, 2019 7:25 am
X, 81, 73, 71, 98, 73, 64
What is the value of X in the above list of 7 numbers?
(1) The average (arithmetic mean) of these 7 numbers is 80.
(2) The range of these 7 numbers is 36.
OA
A
Source: Official Guide
Target question: What is the value of X?
Statement 1: The average (arithmetic mean) of these 7 numbers is 80.
We can write: [m][fraction]X + 81+73+71+98+73+64/7[/fraction]=80[/m]
Multiplyvboth sides of the equation by [m]7[/m] to get: [m]X + 81+73+71+98+73+64 = 560[/m]
At this point, we can see that we COULD solve this equation for X, which means we could answer the target question (but we would never waste time doing so on test day)
Since we can answer the
target question with certainty, statement 1 is SUFFICIENT
Statement 2: The range of these 7 numbers is 36.
Let's arrange the 6 KNOWN values in ascending order: 64, 71, 73, 73, 81, 98
98 - 64 = 34
So the range of the 6 KNOWN values is 34.
To get a range of 36, X can be one of two different values. Consider these two cases:
Case a:
x = 62, which means we get:
62, 64, 71, 73, 73, 81, 98. Range = 98 - 62 = 36 (Perfect!) In this case, the answer to the target question is
x = 62
Case b:
x = 100, which means we get: 64, 71, 73, 73, 81, 98,
100. Range = 100 - 64 = 36 (Perfect!) In this case, the answer to the target question is
x = 100
Since we cannot answer the
target question with certainty, statement 2 is NOT SUFFICIENT
Answer: A
Cheers,
Brent
