is it A?warlock wrote:can anyone explain me this problem
thank you
GMAT PREP Std deviation
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Source: Beat The GMAT — Data Sufficiency |
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kiranlegend
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kiranlegend
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- Thanked: 6 times
A says that 30 % was removed from every tank.. so standard deviation remains the same and it will be 70% of 10 i.e., 7warlock wrote:yes...what is the logic involved?
with B we can't say anything as we don't know individual tank's volumes..
Hi....gotta doubt here with the actual value of the new SD....I know its not required in this problem but just wanna extrapolate
Heres how i approached it
V = Data Value
A = Average
S.D. = Sqrt{(V1-A)^2+(V2-A)^2+(V3-A)^2+(V4-A)^2+(V5-A)^2+(V6-A)^2}/6
Now, as the new values r 70% of the original....the average will also b 70% of the original
Let V' = New data values
& A' = New average value
So, V1' = 70% of V1, V2' = 70% of V2, etc....
So taking 70% common from the equation inside the sqrt,
We will have
New S.D.' = Sqrt (70%) of Old S.D.
Hence new SD=Sqrt(70) of 10...
Is this right...pls correct me if i'm wrong...
Thanks
Heres how i approached it
V = Data Value
A = Average
S.D. = Sqrt{(V1-A)^2+(V2-A)^2+(V3-A)^2+(V4-A)^2+(V5-A)^2+(V6-A)^2}/6
Now, as the new values r 70% of the original....the average will also b 70% of the original
Let V' = New data values
& A' = New average value
So, V1' = 70% of V1, V2' = 70% of V2, etc....
So taking 70% common from the equation inside the sqrt,
We will have
New S.D.' = Sqrt (70%) of Old S.D.
Hence new SD=Sqrt(70) of 10...
Is this right...pls correct me if i'm wrong...
Thanks
