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Road and Railroad Related Rates Problem

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Re: Road and Railroad Related Rates Problem

Re: Road and Railroad Related Rates Problem

Quote:

Originally Posted by

**TheEmptySet** You have the right idea, but when

you train is negative 15 units from the crossing still. The way you set up the equations, the trains crosses when

.

So ten minutes later from then is when

in your model

P.S. I didn't check your algebra or calculus.

So when t = 0, it is negative 15. Was that right when I did 90(t - 10/60).

Cause I'm kind of still confused how my answer is still pretty far off from the actual answer :O

Re: Road and Railroad Related Rates Problem

Quote:

Originally Posted by

**Chaim** So when t = 0, it is negative 15. Was that right when I did 90(t - 10/60).

Cause I'm kind of still confused how my answer is still pretty far off from the actual answer :O

What you have is a right triangle

What you want to find is the rate of change of the hypotenuse.

Then taking the derivative with respect to time gives

So we need to know a,b and c.

The car has traveled 12 miles (a=12) and the train has traveled 9 miles (b=9) and by the Pythagorean theorem c=15.

Plugging all this in gives

Re: Road and Railroad Related Rates Problem

Quote:

Originally Posted by

**TheEmptySet** What you have is a right triangle

What you want to find is the rate of change of the hypotenuse.

Then taking the derivative with respect to time gives

So we need to know a,b and c.

The car has traveled 12 miles (a=12) and the train has traveled 9 miles (b=9) and by the Pythagorean theorem c=15.

Plugging all this in gives

Thanks for replying and showing how you got the answer :)

But just wondering, how did you get 12 and 9 :O