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by CITI29 » Thu Jul 10, 2008 11:31 am
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 rt(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

ans :'e'
some help pls...
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Source: — Problem Solving |

by lion147 » Thu Jul 10, 2008 12:31 pm
Work the equation:

3+ (4/ sq rt(5-x)) = 6

4/ sq rt(5-x) = 3

sq rt(5-x) = 4/3

5-x = (4/3)^2

5-(16/9) = x

x = 3.222.. = 3.2 to the nearest tenth.
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