Lately I've been pressure washing some houses and a few driveways. I just charge whatever and have done some for free because, well, I'm too nice. I pressure washed a 100'x30' rectangle driveway yesterday and the standard is .20-.30 per square foot for driveways. Not that I use that method. It's just standard. I started thinking what if it was a semi-circle driveway but not actually a true half circle, so ((3.14)r^2)/2 minus the inside would not work. I thought how in the heck could I find out the area of the drive way. When I thought if I treat the driveway as the positive quadrant of a graph I could figure it out. These are hypothetical numbers just to show the process. For example I could measure from end to end of the outer most edge of the driveway and let's say it's 100'. That would be 0'-100'. Now do the same for the inner most edge of the driveway and let's say it's 90'. That would be 0'-90'. Now if I go to the center of the 100' and measure up to the tallest point of the arch and let's say it's 30'. Now do the same for the 90' and say it's 20'. Now I know that sense the function of the graph only has one curve it's a squared function. So basically if I take the integral of the outer function and minus the integral of the inner function it should give me the area of the driveway. So it would be integral 0'-100' of x^2+30 Minus the integral 0'-90' of x^2+20 http://images-77.har.com/e1/mediadisplay/77/hr3148277-2.jpg I believe this is correct. I took advanced placement calculus in high school, which is basically college level but our teacher said it was more thorough and more difficult. I made an A+. It was my favorite math and I was just thinking the other day that I would like to take a refresher course.