SOLUTION: my question is: find the area of the ring in the cross section of a pipe with an outer diameter of 4 inches and an inner diameter of 2 inches. my next question is: the minute ha

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Question 13124: my question is: find the area of the ring in the cross section of a pipe with an outer diameter of 4 inches and an inner diameter of 2 inches.
my next question is: the minute hand of a tower clock is 6 feet long. what distance will the extremity move over in 36 minutes?

my next question is: find the length of one side of the largest square timber which can be cut from a log 24 inches in diameter?
my next question is: if an automobile wheel has a diameter of 28 inches, how many revolutions per minute will the wheel make when the automobile is going 60 mph?
my next question is: if the diameter of a piston is 30 inches, find the total pressure on the piston when the pressure of steam is 100 lbs per square inch.
Answer by glabow(165) About Me  (Show Source):
You can put this solution on YOUR website!
I am going to assume that you know the area of a circle is PI+%28r%5E2%29
So, if you know the r (radius) you can calculate the area. Sometimes it is better not to multiply out by PI (3.14159) but just leave it as PI.
Your first question has a diameter of 4 on the outside, and a diameter of 2 on the inside. If you could find the areas of both of these circles, could you find the area of the ring? Try subtracting the area of the inner circle from the area of the outer circle!
Also, remember the diameter is twice the radius. So, putting this all to work:
The area of the outer circle is PI%28r%5E2%29=PI%282%5E2%29=+PI%284%29
The area of the inner circle is PI%28r%5E2%29=PI%281%5E2%29=PI
The area of their difference is PI%284%29-PI=PI%283%29
Your second question is similar except here you are dealing with the circumference of a circle, which is 2%28PI%29r
You know what r is (6), so how far will the tip move in one hour? This is the circumference of the circle with a radius of 6. [Do the math]
But we want to know how far it moves in 36 minutes. Well, the hour is 60 minutes, so the part of the hour that the tip moves is 36/60 of the whole circumference. [Do the math] Do you get PI%2836%2F5%29?