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irritating quest..types...

by willbeatthegmat » Fri Feb 06, 2009 9:53 am
Reserve tank 1 is capable of holding z gallons of water.Water is pumped into tank 1, which starts off empty, @ x gall/min.tank 1 simultaneously leaks water @ y gall/min(where x>y). The water that leaks out of tank 1 drips into tank 2, which also starts out empty. If the total capacity of tank 2 is twice the num of gallon tat remain in tank 1 after 1 min, does tank 1 fill up before tank 2?

1)zy< 2x^2-4xy+y^2 {(&#8730;2x+&#8730;2y)^2}
2)the total capacity of tank 2 is less than one-half that of tank 1.


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by sureshbala » Fri Feb 06, 2009 3:08 pm
Dear friend the first statement is not clear to me....Anyway here is the solution.

Capacity of Tank 1 = z

Amount of water in Tank 1 after one minute = x-y (since in one minute x gallons are pumped into the and in the same one minute y gallons are emptied into Tank 2)

Given that capacity of Tank 2 = 2(x-y)

It is clear that Tank 1 is effectively filled at the rate of (x-y) gallons/minute and Tank 2 is filled at the rate of y gallons/minute

So time taken to fill Tank 1 = z/(x-y) and time taken to fill Tank 2 = 2(x-y)/y

Now the question: Is z/(x-y) < 2(x-y)/y

i.e Is zy < 2x^2 - 4xy + 2y^2.

So the first statement must be sufficient to answer this.

Statement 2(x-y) < z/2

i.e 4(x-y) < z

Clearly this is not sufficient to answer.
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