Function Question

[tlwaring]

We received a problem in class today I can't figure out:

"Suppose the circumference of the earth at the equator is thr function (in terms of the radius r) C(r)=2(pi)r
Suppose 1 foot is added to the end of a string that fits tightly about the equator and that string is held evenly above the surface of the earth. The new circumference (in terms of radius x) is N(x)=2(pi)x or just C(r)+1 foot.
Without finding a number for either r or the new radius x, find an expression that tells whether a mouse could run under the lengthened string."

Can anyone explain this to me, and show me how to set it up?

Thanks -

 

[stapel]

A good start would be to plug "C + 1" in for "C", and solve for "r=".

Eliz.

 

[chandamcarter]

solving word problems

Tommy walks across a train bridge. He gets 2/3 of the way across and see the train comming toward him. He calculates that if he keep running forward that he can barely beat the train or he could go the opposite direction and beat the train. If he runs at a average speed of 8mph, how fast is the train going?

 

[chandamcarter]

solving word problems

Would this be the correct formula to use? d=r*t

 

[stapel]

Re: solving word problems

Tommy walks across a train bridge....

I'm sorry, but I must be missing something. How does this relate to the question at hand?

Please reply with clarification. Thank you.

Eliz.

 

[galactus]

Since the new circumference is just 2*pi*x and this is one foot more than 2*pi*r, we could equate 2*pi*x=2*pi*r+1.

Solve for x to find the new radius x in terms of the old radius r. You'll see x is equal to r plus 'something'. Since we're using feet, is this 'something' enough for a mouse to run under?.