## Sunday, January 16, 2011

### Cameron's Final Percent Post

A percent means out of 100, also another name for hundredths and can be expressed as decimals or fractions.

Representing percents

Shade squares on a grid of 100 squares called a hundred grid to represent a percent. A completely shaded grid represents 100%. If you shade more than one grid, that represents a percent greater than 100%. To represent a fractional percent between 0% and 1%, you have to shade part of one square. Also, to represent a fractional percent greater than 1% you have to shade squares from the hundred grid to show the whole number, then shade part of a square from the grid to show the fraction.

Fractions, Decimals, Percents

Percents can also be represented as a decimal or a fraction.
Eg. 80% = 0.8 = 4/5

Percent of a Number

You can use mental math strategies such as doubling, halving, and dividing by 10 to find the percents of some numbers. Write the percent as a decimal and then multiply by the number to calculate the percent of a number.
Eg. 14 1/2% of 60 = 0.145x60 = 8.7

Combining Percents

Adding percents can solve problems, for example; 5% + 6% = 11%.

To calculate the increase in a number, add the combined percents to the original number.
Eg. 15% of 100 = 0.15x100=15, 100+15=115
Or multiply the original number by a single percent greater than 100.
Eg. 115% of 100 = 1.15x100 = 115

Percents of percents can be used to determine amounts that result from
consecutive percent increases or decreases.

Percent review video: