The second common type of problem is to compare two known ratios. The challenge here is that the bases of comparison are usually different, making comparisons difficult. Ratios handles this by giving the three logical comparisons:

1. 1)Showing the “per lower unit” basis
   

2. 2)Using the first ratio’s lower as the basis
   

3. 3)Using the second ratio’s lower as the basis
   

Working Example:

Is $25 for three light bulbs a better value than a competitive package priced at $39 for five?

Both ratios are known. The screenshots and captions below explain the process:

Compare - Setting up the problem:

When setting up a compare, it is very important for units to be consistent. It the example above, the upper blocks are in dollars and the lower blocks are in loads. We are comparing $ per load, so both ratios need $ in the upper blocks and loads in the lower blocks.

Other examples:

Continuing:

A new comparison with the first ratio can be made by touching the red blocks or by touching the large red “C” button once. Pressing the upper gray block or clear [C] twice allows a new problem to be entered.