



 
Kenneth, For the example you give of $\$720$ for 92 days at 7% based on 360 days the conventional calculation would be to find 7% of $\$720,$ which would be for 360 days and then multiply by 92/360 since you only used 92 of the 360 days. This would give
In the percentday method the multiply the 7 and 92 first to get
Since $\$720/100 = \$7.20$ the resulting calculation is $\frac{644}{360} \times \$7.20 = \$12.88.$ I hope this helps,  


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