Two parallel sides of a rectangle are being lengthened at the rate of 2 in/s while the other two sides are shortened in such a way that the figure remains a rectangle with constant area A = 50 in^2. What is the rate of change of the perimeter when the length of an increasing side is 5 in.?

Question

aivantettet26 · Answer

my first guess is 0
my second is 20 ft/s

anonymous · Answer

Let me look at it.

anonymous · Answer

Give me a few.

anonymous · Answer

Ok Sorry. THe answer I get is neither of those. Consider two keep facts. $$A=50in^2 = lw$$ and $$P=2w+2l$$. Now let's arbitrarily assign w to be the dimension that is increasing in size and thus l is decreasing in size. So, use the first formula to determine a value of l in terms of w. You can substitue that into the second formula so that only P and w will be left. Then differeniate that formula with respect to t and substitute in the given values and you should arrive at a decreasing rate that falls somewhere between 0 and -10 in/sec.

anonymous · Answer

Let me know what you come up with. I would be happy to review you work as well.

aivantettet26 · Answer

sorry but ill closed this question for now :)