 Montana Council of Teachers of Mathematics # Please Ask My Dear Aunt Sally

Dear Aunt Sally,

My students are having trouble setting up and solving percent problems such as “7 is 28% of what number?” Do you have any suggestions?

Signed,
Di Lemma

Dear Di,

I have taught this topic two ways. One way is to write the word sentence and then write the numbers underneath the numbers, put a multiplication sign underneath the word “of”, an “=” sign under the word “is” and put a “n” for the unknown. Then solve the equation. In my experience, this method works well with students proficient in solving equations and a good understanding of the meaning of percent. With average students, I have been more successful with something called the “is over of” method using proportions. You use the formula “is over of is equal to percent over 100”. The words “of” and “is” have a number associated with it in the word sentence (usually the number next to the word). Then solve using cross products. I like this method better for several reasons. The best reason is that students have less trouble! Another good reason is that it helps students understand that percent means “out of 100”. I also recommend that if the unknown is the percent I use a “p” instead of an “n” for the variable so the students remember to put a “%” sign on their answer. Try it and I am sure you will like it.

Signed,
Your Dear Aunt Sally

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