Percentages

Percentages are a way of expressing a fraction, a part of a whole, as an appropriate portion of 100. The relation is written out as the equation to the right of the Percent Gauge:

Part/Whole = Percent/100

With this virtual manipulative you may specify any two of the three quantities, "Part," "Whole," or "Percent." When you click the Compute button, the computer will calculate the remaining quantity. The percentage relationship is displayed visually in the vertical column of the Percent Gauge and in a pie chart. An equation shows how to compute the unknown quantity, and the result is stated verbally.

Three examples illustrate the kinds of computations involved:

1. 17 is what percent of 85?

   Enter 17 as the Part and 85 as the whole and press Compute.
   Solving for the Percent in the displayed equation, we see % = 100x17/85, so "17.0 is 20.0 of 85.0," and 20/100 is shown in red in the Percent Gauge and in blue in the pie chart.

2. What is the sale price of a $75 dress if there is a 30% reduction?

   With a 30% reduction, the sale price will be 70% of $75, so we enter 70 in the % box and 75 as the Whole and Compute. The Percent Gauge shows that 70% of 75 is 52.5, indicating a sales price of $52.50.

3. If a score of 48 on a test was 75%, what total was possible?

   Here we know the Part and Percent: Press Reset, enter 48 as the Part and 75 as the Percent and Compute. The Percent Gauge shows that 75% of 64 is 48, so that 64 was the maximum possible score.