Water Tanks

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Water Tanks

by csandeepreddy » Mon Oct 20, 2008 6:16 pm
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.

OA A
Source: — Data Sufficiency |

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by stop@800 » Mon Oct 20, 2008 11:36 pm
A
We know all volumes became .7v
so its just like multiplication by a constant
so SD will also change accordingly

we know how much mean got deviated
and how much each number got deviated
so SUff



B
mean changed
but we do not know how much each number got deviated from mean so insuff