The two most common forms of percent problems are as follows.

(1) What is 20% of $80?

(2) 50 is what percent of 200?

You should practice these types of problems until they are clear in your mind and you are an expert at both types. When you master these two types of problems, you will be surprised at how many types of real-life problems become easier for you.

Internet sales increased by 12.6% in 2010, resulting in $165.4 billion in sales for the United States. Reports indicate that e-commerce will continue to grow 10% per year from 2010 to 2015. What percent of your purchases do you buy online?

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1. To answer this question, you need to estimate the retail price of a major appliance. Let's say that this is $1000.

   

   This is the estimated lost sales tax per appliance. With 10,000 appliances, the total lost sales tax per year would be around $650,000.

2. The population of the United States is about 310 million. With untaxed purchases of $500 per person per year, the annual total of untaxed purchases is about

   

   Suppose that the average sales tax rate is 6%. This would be a total lost sales tax revenue of about $9.3 billion for one year.