# About Formulas

## Opening

# About Formulas

You may already know the formula for the area of a rectangle: *A* = *lw*.

A formula is a mathematical way of writing a rule for computing a value. The formula *A* = *lw* says that to find the area of any rectangle, multiply the rectangle’s length by its width. Today, you’ll revisit four rate situations and write formulas for them.

- How can you express speed as a formula?