A method to estimate planar areas for simple or complex shapes is described. The method relies on the use of weighing the area of interest and using proportional constructs.

In the days before calculators and personal computers an engineer always had a slide rule nearby. These days it is difficult to locate a slide rule outside of a museum.

I don't know how many of those who have used a slide rule ever thought of it as an analog computer, but that is really what it is. As such, the slide rule can be used to teach the modern view of the relationship between nature and mathematics and about the formalization of this concept known as isomorphism, which is one of the most pervasive and important concepts in mathematics.

This simple example shows how algebra can be useful in the real world: Should Grandpa start receiving his Social Security Benefits at age 62 or should he wait until age 65?