Predict the result
Find the commission rate when 43000 dollars in sales earns 1720 dollars in commission.

Set up the model
Divide the commission by the total sales.
Convert the resulting decimal to a percent.

Work the example
Seventeen hundred twenty divided by forty three thousand is zero point zero four.
The commission rate is four percent.

Check the result
How long earns 720 dollars simple interest on 4000 dollars at six percent per year?
Take eight seconds to think before the answer appears.
[Eight-second silent pause to work; the answer remains hidden.]
The time is three years, using simple interest at the stated annual rate.

Interpret the result
Simple interest uses principal times annual rate times years; it is not compound interest.