# Question Video: Solving Word Problems Involving Percentages Mathematics

Determine the total cost for a shirt if its regular price is \$24 and the sales tax is 7 1/2%.

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### Video Transcript

Determine the total cost for a shirt if its regular price is 24 dollars and the sales tax is seven and a half percent.

As there is a sales tax of seven and a half percent, we need to work out this percentage of 24 dollars and then add on our answer. Let’s firstly consider how we can work out seven and a half percent of any value. Seven and a half percent is the same as 7.5 percent. We could calculate this by working out 75 percent and then dividing this by 10, as 75 divided by 10 is equal to 7.5. Alternatively, we could work out five percent and 2.5 percent and add these values. To get from five percent to 2.5 percent, we would need to halve the value or divide it by two.

Let’s consider the regular shirt price in this case of 24 dollars. 100 percent is equal to 24 dollars. We can calculate 50 percent by halving this value or dividing by two. 24 divided by two is equal to 12. Halving this number again would give us the value for 25 percent, as 50 divided by two equals 25. 12 divided by two is equal to six. Therefore, 25 percent is equal to six dollars. 50 plus 25 is equal to 75. Therefore, 75 percent is equal to 18 dollars, as 12 plus six equals 18. Dividing 18 by 10 gives us 1.8. Therefore, 7.5 percent is equal to one dollar and 80 cents.

We could also have worked this out by firstly finding 10 percent. 100 divided by 10 is equal to 10. 24 divided by 10 is equal to 2.4. Therefore, 10 percent equals two dollars and 40 cents. Halving this tells us that five percent is equal to one dollar and 20 cents. Halving this again gives us that 2.5 percent is equal to 60 cents. Adding these two values once again proves that 7.5 percent is equal to one dollar and 80 cents.

We need to calculate the total cost of the shirt. We do this by adding 24 dollars and one dollar 80 cents, the regular price plus the sales tax. Adding these values gives us 25 dollars and 80 cents. This is the total cost for the shirt once the sales tax has been added.