Wednesday

December 17, 2014

December 17, 2014

Posted by **bekah** on Sunday, January 2, 2011 at 11:32am.

The length of a rectangle is increasing at 3 ft/min and the width is decreasing at 2 ft/min. When the length is 50 ft and the width is 20 ft, at what rate is the rectangle decreasing?

- calc -
**Reiny**, Sunday, January 2, 2011 at 12:00pmLet the width of the rectangle be x ft

let the length of the rectangle be y ft

Area = xy

d(Area)/dt = x dy/dt + y dx/dt

given: dx/dt = -2 and dy/dt = 3

so when x = 20 and y = 50

d(Area)/dt = 20(3) + 50(-2)

= -40

At that moment, the area is**decreasing**at a rate of 40 ft^2/min

- calc -
**bekah**, Sunday, January 2, 2011 at 12:06pmthank you so much!!!!

**Answer this Question**

**Related Questions**

College Algrebra Math 133 unti 1 IP 1 - Suppose the width of a rectangle is 5 ...

calculas - if the length is decreasing at a rate of 2 in./min. while width is ...

math - Suppose that the width of a rectangle is 5 inches shorter than the length...

Calculus - The length of rectangle is increasing at a rate of 8cm/s and its ...

Algebra/geometry - a rectangle has a width of 4 cm less than it's length. if a ...

math - the length of a rectangle is 7 times as long as its width. if the ...

algebra , help - Can someone help me set up the equations thanks. Directions: ...

Calculus - Assume the dimensions of a rectangle are continuously changing in a ...

Math - A norman window is constructed by adjoining a semicircle to the top of an...

Alg II - I have a rectangle whose sides are in the proportion b:a, where b is ...