|
|
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.
Customized
for You
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
08 Jun 2022, 11:32
Kudos
Bookmarks
D
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
95%
(hard)
Question Stats:
37% (01:59) correct
63%
(01:23)
wrong
based on 123
sessions
History
Date
Time
Result
Not Attempted Yet
What is the standard deviation of the three numbers \(x\), \(y\), and \(z\) that have an average (arithmetic mean) of 7?
(1) \(x\)\(^2\) + \(y\)\(^2\) + \(z\)\(^2\) = 174
(2) The standard deviation of the 3\(x\) - 5, 3\(y\) - 5 and 3\(z\) - 5 is 9
(1) \(x\)\(^2\) + \(y\)\(^2\) + \(z\)\(^2\) = 174
(2) The standard deviation of the 3\(x\) - 5, 3\(y\) - 5 and 3\(z\) - 5 is 9
11 Sep 2022, 20:56
Kudos
Bookmarks
Given 3 numbers x,y and z have a mean of 7. We need to find the standard deviation.
Standard deviation by formula will be square root of average difference squares of each term to that of mean.
SD=√((7^2-x^2)+(7^2-y^2)+(7^2-z^2)-14(x+y+z))/3
We can modify this as SD=√((3*7^2)-(x^2+y^2+z^2)-14(x+y+z)/3
Statement 1:
Gives the value of x^2+y^2+z^2. We can calculate SD. Also x+y+z=21 as per the stem.SUFFICIENT.
Statement 2: adding or subtracting same value from the list members will not impact sd while multiplying by 3 will have SD multiplied by 3. We can find SD. SUFFICIENT
ANS: D
Posted from my mobile device
Standard deviation by formula will be square root of average difference squares of each term to that of mean.
SD=√((7^2-x^2)+(7^2-y^2)+(7^2-z^2)-14(x+y+z))/3
We can modify this as SD=√((3*7^2)-(x^2+y^2+z^2)-14(x+y+z)/3
Statement 1:
Gives the value of x^2+y^2+z^2. We can calculate SD. Also x+y+z=21 as per the stem.SUFFICIENT.
Statement 2: adding or subtracting same value from the list members will not impact sd while multiplying by 3 will have SD multiplied by 3. We can find SD. SUFFICIENT
ANS: D
Posted from my mobile device
11 Aug 2025, 13:48
Kudos
Bookmarks
Automated notice from GMAT Club BumpBot:
A member just gave Kudos to this thread, showing it’s still useful. I’ve bumped it to the top so more people can benefit. Feel free to add your own questions or solutions.
This post was generated automatically.
A member just gave Kudos to this thread, showing it’s still useful. I’ve bumped it to the top so more people can benefit. Feel free to add your own questions or solutions.
This post was generated automatically.
