Video: Solving Word Problems Involving Percentages

Benjamin wants to buy new rollerblades. The price of a pair of rollerblades is $78, and the sales tax is 7%. Determine the total cost of the rollerblades.

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Video Transcript

Benjamin wants to buy new rollerblades. The price of a pair of rollerblades is 78 dollars and the sales tax is seven percent. Determine the total cost of the rollerblades.

Sales tax is an additional cost that you have to pay on top of the price of an item. The total cost of the rollerblades is equal to the price of the rollerblades plus the value of their sales tax. The price of the rollerblades is 78 dollars and the sales tax is seven percent of this — seven percent of 78 dollars. We need to work out how much the sales tax comes to.

We’ll consider one method using a calculator and one method without using a calculator. First, the noncalculator method: one percent of 78 dollars is equal to 78 dollars divided by 100. It’s 0.78 dollars or 78 cents. To find the value of seven percent, we can multiply this by seven: 78 dollars over 100 multiplied by seven. We can evaluate this multiplication using a column method. 78 multiplied by seven is equal to 546. So the calculation is equal to 546 over 100, which is five dollars and 46 cents.

This remember is the noncalculator method for calculating the sales tax. Now, let’s consider a calculator method. When we see the word “of” in a question about percentages, it means multiply. Seven percent of 78 dollars is the same as asking for seven percent multiplied by 78 dollars.

Percent means out of 100. So we can replace seven percent with seven over 100. Now, we can use a calculator to perform this calculation. Just as in our noncalculator method, it’s equal to five dollars and 46 cents.

Therefore, the total cost of the rollerblades is equal to the price 78 dollars plus the sales tax five dollars and 46 cents. The total price is 83 dollars and 46 cents.

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