What's the fastest way to do these math problems?

Senior0991
Fri, 31 Jul 2009 17:50:01 +0000

Because circumference=2pir, the circumference of the larger circle is twice that of the smaller circle (all that changes in the above equation is radius). Thus, the circumference of the smaller circle is 18. Then, you know the arc will be 80/360 of the entire circumference (360, if you notice, is the angle of the entire circumference, 80 is the angle accross from the desired arc). So, the arc length is 18*(80/360)=180/45=4 units.

I did this before looking at your response… So, it looks like you did it the fastest way for your second method.