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Hi Lets get some math head do this.?
A railroad curve is laid out on a circle. What radius should be used if the track is to change direction by 20 degrees in a distance of 100 miles?
To approximate the speed of the current of a river, a circular paddle wheel with a radius of 4 feet is lowerd in to the water. If the current causes the wheel to rotate at the speed of 10 revolutions per minute, what is the speed of the current? (answerd expressed in miles per hour)
I know this is semi cheating but please forgive me..I don't do this if you take a look at all my question but I need an answer fast and my math is not the best 
For your first question, since a circle is 360°, and you are going to change 20°, take 360°/20°. This give you 18 "sections", each 100 miles. Multiply 18 by 100 to get 1800 miles. So the circumfrence of the circle is 1800 miles. C = (2)(pi)(r). Plug in 1800 for C and solve for r(adius) to find that the radius is approximately 286.48 miles.
For the second question, you need to find the circumfrence of the wheel. C = (2)(pi)(4) = approximately 25 feet. So, if the wheel spins 10 times, then it "travels" 250 ft per minute. Multiply by 60 minutes, and the speed of the river is 15,000 ft per hour. Since there are 5,280 feet in a mile, divide 15.000 by 5,280 to get 2.84 miles per hour.