- #1

coolkid800

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A water trough is 15 feet long, and its cross section is an equilateral triangle with sides 3 feet long. Water is pumped into the trough at a rate of 10 cubic feet per second. How fast is the water level rising when the depth of the water is 1/2 foot?

( Hint: First, what is the height h of an equilateral triangle of side length s? Next, what is the area of an equilateral triangle in terms of the side length s? Then write the area in terms of h. The volume of the water in the trough at time t is the product of the cross-sectional area with water and the length of the trough. )

a) What is the height h of an equilateral triangle of side length s?

h = ____ ft.

**Note: Answers I said were (3*sqrt(3))/2 and 1/sqrt(3) I thought all I had to do was the pythagorean theorem...but apparently its not the answer**

b) The water level is rising at a rate of __(2*sqrt(3))/3 ft./sec.__