Problem:
A girl flies a kite at a height of 300ft, the wind carrying the kite horizontally away from her at a rate of 25 ft/s. How fast must she let out the string when the kite is 500 ft away from her?
The correct answer is 20ft/s
My procedures
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Can anyone tell me what I did wrong?
I have told you exactly how to do it but you have chosen to ignore what I posted.
Furthermore, you said "How fast must she let out the string when the kite is 500 ft away from her?"
when clearly the given answer requires "... the kite is [400] ft away from her?"
Using 400 ft and what I posted, the correct answer falls out in a couple of lines.
Hello.
Just to post the solution...
You were right mr fantastic, it was indeed using that formula. For a moment I thought all related rates problems could only be solved using trig relationships, that's why I kind of "ignored" your solution. My apologies for that.
The problem can be solved with the values in this picture:
And taking the derivative with respect to t of both sides of the following equation:
Can be solved in an easier way by taking the derivative of both sides from the following equation and solving:
Even though I didn't use your solution because by that time I DIDN'T KNOW about the usage of the quadratic formula for solving these problems, I thank you for having tried to help. If I did know about it, then I would probably solved the problem using your solution.