Quick! What's the square root of two? What's 1/2 plus 1/3? The value of Pi? 15% of 60? The area of a rectangle 15 x 20 feet? The sine of 30 degrees? How can I layout a rectangle and be sure the comers are square? Who knows, you say? Who cares, you say? Well, do you ever eat at a restaurant? Have you ever bought a rug? Built a house, or at least helped to build something? If so, you've needed the skills to answer questions like these. These are not esoteric skills that you learned in school and never think of again. There are people who need these skills every single day! Most likely, you're one of them … especially if you earn your living with computers.