[siddharthaduggirala]

Originally Posted by Mcnabb_ISB

Ellen can purchase a certain computer at a local store at price of p dollars and pay 6% sales tax. Alternatively, Ellen can purchase same computer from catalog for q dollars including everything. Will it cost more for Ellen to purchase from local store or catalog?

1) q - p <50
2) q = 1,150

please explain

My explanation:

Total cost at local store is 1.06*p

Consider 1:

q-p<50

two unknowns and one equation. so not suff

Consider 2:

q=1150

No info abt p so no suff


take both

now we have

1150-p<50 => p>1100

consider p=1101

now total cost is 1.06*1101=1167.06

so from this we know that purchasing at local store is costlier than purchasing at catalog.

so ans is C

[Arijit sen]

During an experiment, some water was removed from each of 6 water tanks. If the standard deviation of the volumes of water in the tanks at the beginning of the experiment was 10 gallons, what was the standard deviation of the volumes of water in the tanks at the end of the experiment?

1) For each tank, 30 percent of the volume of water that was in the tank at the beginning of the experiment was removed during the experiment.

2) The average (arithmetic mean) volume of water in the tanks at the end of the experiment was 63 gallons.

I found this is one of the earlier threads but the soln wasn't there. Please provide the explaantory soln.

Thanks.

[siddharthaduggirala]

Originally Posted by Arijit sen

During an experiment, some water was removed from each of 6 water tanks. If the standard deviation of the volumes of water in the tanks at the beginning of the experiment was 10 gallons, what was the standard deviation of the volumes of water in the tanks at the end of the experiment?

1) For each tank, 30 percent of the volume of water that was in the tank at the beginning of the experiment was removed during the experiment.

2) The average (arithmetic mean) volume of water in the tanks at the end of the experiment was 63 gallons.

I found this is one of the earlier threads but the soln wasn't there. Please provide the explaantory soln.

Thanks.

IMO A

since the same amt of water was removed from each of the tank the SD remains same so A alone is sufficient.


2) gives the avg. this is not sufficient to determine the SD

So A

Puys any alternative expln?

[bhavin422]

Originally Posted by siddharthaduggirala

IMO A

since the same amt of water was removed from each of the tank the SD remains same so A alone is sufficient.


2) gives the avg. this is not sufficient to determine the SD

So A

Puys any alternative expln?

Good question arijit ...
Hey siddharth , i guess statement in bold is incorrect ..

Yes, SD does not change for equal amount of changes in every qty, however question reads equal change in percent, which does not translate to equal amounts unless initial quantities are same ...
Equal % change also changes the SD by same % of original ..
So SD = 70% of 10 = 7

St 2 : old deviation and new average is not enough to calculate new SD ..Not suff ..

Ans A

[siddharthaduggirala]

Originally Posted by bhavin422

Good question arijit ...
Hey siddharth , i feel statement in bold is incorrect ..

Yes, SD does not change for equal amount of changes in every qty, however question reads equal change in percent, which does not translate to equal amounts unless initial quantities are same ...So, 1 alone is not sufficient ...

Still not sure about the soln ...I guess it should be E ...
I guess, only new avg and equal % change still does not give us original values ...Should be E ...though dicy about this part ...

Yaa the thought had occured to me. But some how chose A. So I think the ans should be E

[bhavin422]

Originally Posted by siddharthaduggirala

Yaa the thought had occured to me. But some how chose A. So I think the ans should be E

Sorry dude :(...i have edited my post now...though SD does not remain same , we still have a definite SD from St 1 ...

I guess the answer is A ...not very sure this time..

[siddharthaduggirala]

Originally Posted by bhavin422

Sorry dude :(...i have edited my post now...though SD does not remain same , we still have a definite SD from St 1 ...

I guess the answer is A ...not very sure this time..

Yaa since the same 30% is taken out from all the vessels. So we need not worry abt the initial quantity in the vessels. So the SD remains the same.

What say puys???

[bhavin422]

Originally Posted by siddharthaduggirala

Yaa since the same 30% is taken out from all the vessels. So we need not worry abt the initial quantity in the vessels. So the SD remains the same.

What say puys???

hey siddharth ...both of us agree that st 1 is sufficient for different reasons

Yes, since its DS we need not worry what is the exact new SD as long as we know only 1 values is poss ...

However SD does not remain same ...Infact it changes by the same percentage ...

Let me take a simple eg to prove my point
Let there be just 2 vessel with qty 10 and 30 Hence avg = 20 and SD =10
30% reduction
New qty are 7 and 21 , avg = 14 ; new SD =7

I.e new SD = 70 % original SD ...its not the same !!

[siddharthaduggirala]

Originally Posted by bhavin422

hey siddharth ...both of us agree that st 1 is sufficient for different reasons

Yes, since its DS we need not worry what is the exact new SD as long as we know only 1 values is poss ...

However SD does not remain same ...Infact it changes by the same percentage ...

Let me take a simple eg to prove my point
Let there be just 2 vessel with qty 10 and 30 Hence avg = 20 and SD =10
30% reduction
New qty are 7 and 21 , avg = 14 ; new SD =7

I.e new SD = 70 % original SD ...its not the same !!

Then in that case the ans must be E since we cannot calculate the SD after the change in volume. is it not?

[bhavin422]

Originally Posted by siddharthaduggirala

Then in that case the ans must be E since we cannot calculate the SD after the change in volume. is it not?

Why do u say so buddy ?
from the question we have original SD of 10 ..

St 1: My point was (somebody correct if its wrong) 30 % reduction of each value ,reduces new mean by 30 % and hence also the SD is reduced by 30 % ...So new SD = 7 ...Sufficeint ...Ans A

P.S : i am loving the cross correction, it only helps to get better !! ..Pls correct me again dude ..

Cheers

P.S :This post also makes me hardcore Pagal !!