Percents+in+the+Real+World

Students have difficulties applying percents to real world examples.

Ask students where are some of the places they have seen percents?
 * While shopping - clothes
 * Sales receipt
 * Assignments - grades

Emphasize again that a percent means per 100 - explain that when a student gets a test back and it is marked 80% that means that had there been 100 questions on the test the student would have gotten 80 out of 100 correct. Likewise if something is 10% off it means: 10 dollars per 100 dollars so if a prom dress cost $100 and there was a sale of 10% off then it would cost $90. If the sale was 28% then the dress would cost $72. We must consider that not every test we take has 100 question or every dress is $100. How do we find 15% of $30 or how many questions did I get right if I missed 15% of the questions on a 30 question test (meaning I got an 85%)? These answers can be found several ways - first we can consider 10% of 30 - if % means per 100 then 10% can also be written as 10/100 or 1/10 when it is reduced. Ask your self what is 1/10 of 30? The answer is 3. We now know that 3 is 10% of 30. What would 5% of 30 be? It would be one half of 10% or 1.5 This means that I would save $4.50 dollars if an item was 15% off of $30. Or I would have missed 4 1/2 questions on the test in order to get an 85%. See Finding a percent of a number starting with 10% for a further example.

We use the same methods to figure sales tax. Even though the cash register does this figuring for us we should now how to quickly estimate how much tax will be on our purchase so we can have an approximate total in our mind when we are paying.

You will need to stop the following clip to allow students to do computations at the appropriate times. Real World Math Breakfast

For an assessment give students a variety of shopping adds and send them shopping for Mother's day presents. Have them always pay the highest price listed before taking off the discounted price. They will also need to figure in Sales tax 6.5% for Utah. Check students work to unsure they have a clear understanding of how to figure percents in the real world. Have students work on mental math and figure the answer without paper pencil. Also discuss with students what is a reasonable answer would be - for example an unacceptable answer would be $5 + tax.