Using Percent Bars

Post date: Oct 13, 2011 11:35:29 PM

Percent bars are a great tool to get students to think about finding the percent of a number or about estimating what percent a part is of a whole. These bars are a great way to get students to start reasoning proportionally, which is a huge shift in thinking for middle school students. I have attached a file which attempts to demonstrate how a student might use a percent bar to find 39% of 320. The "student work" is in a blue font.

In general, students that are reasoning with percents should become fluent using benchmark percents such as 50%, 25%, 10%, and 1%. Students can use these benchmarks to build up to or down to the number they are trying to find. Finding these benchmarks can be somewhat easy since 50% is half of a number, 25% is half of that, 10% of a number is found by moving the decimal one place to the left and 1% can be found by moving the decimal two places to the left.

On Monday, we discussed several strategies for comparing ratios without converting them all to percents.