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# The concentration of a certain chemical in a full water tank

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The concentration of a certain chemical in a full water tank [#permalink]

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25 Mar 2004, 12:05
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

The concentration of a certain chemical in a full water tank depends on the depth of the water. At a depth that is x feet below the top of the tank, the concentration is 3+(4/sq root(5-x) )parts per million, where 0 < x < 4. To the nearest 0.1 foot, at what depth is the concentration equal to 6 parts per million?

(A) 2.4 ft
(B) 2.5 ft
(C) 2.8 ft
(D) 3.0 ft
(E) 3.2 ft

Vivek.
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25 Mar 2004, 12:14
E for me
I think you just have to set (4/sq root(5-x) ) = 3
Isolate x and you get x=3.22
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25 Mar 2004, 12:14
vivek_dj wrote:
The concentration of a certain chemical in a full water tank depends on the depth of the water. At a depth that is x feet below the top of the tank, the concentration is 3+(4/sq root(5-x) )parts per million, where 0 < x < 4. To the nearest 0.1 foot, at what depth is the concentration equal to 6 parts per million?

(A) 2.4 ft
(B) 2.5 ft
(C) 2.8 ft
(D) 3.0 ft
(E) 3.2 ft

Vivek.

3.2 feet

Equated the given equation to 6.
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25 Mar 2004, 14:08
I kind of did a calculated guess......please lemme know if you all think it's right or wrong:
Since the deepest point would be 4 ft, plugging in x = 4 would give us 7ppm as the concentration. So we narrow anser to D & E.........if we plugin 3 ft then we get 5.25 ppm, hence E should be the answer....wotsay folks???
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25 Mar 2004, 14:45
cbrf3 wrote:
I kind of did a calculated guess......please lemme know if you all think it's right or wrong:
Since the deepest point would be 4 ft, plugging in x = 4 would give us 7ppm as the concentration. So we narrow anser to D & E.........if we plugin 3 ft then we get 5.25 ppm, hence E should be the answer....wotsay folks???

Nice Absolutely good
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Paul

25 Mar 2004, 14:45
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