## Monday, January 17, 2011

### Final Percent Post

What is a percent?
A percent is a value out of 100, that can be expressed as a decimal, and a fraction. It is also another name for "hundredths".

- ex. 65% means 65 out of 100 or 65/100 or 0.65

Representing Percents (4.1)
To represent a percent, you can use hundred grids because they are out of 100.

- ex. 65%

Fractions, Decimals, and Percents (4.2)
Percents can be represented as fractions and decimals. To convert a percent to a decimal, you must divide the percent by 100. To convert a decimal into a fraction, you write the decimal as the numerator. However, the denominator depends on the place value of the decimal.

eg.
decimal = 0.003 -> fraction = 0.003/1000 (because the 3 is in the thousandths place)
decimal = 5.98 -> fraction = 5.98/100 (because the 8 is in the hundredths place)

Now when the denominator is set, you must multiply the numerator until it becomes a whole number (or multiply it by the denominator).

eg.
0.003/1000 -> 0.003 x 1000 = 3/1000
5.98/100 -> 5.98 x 100 = 598/100

Lastly, you must simplify your fraction.

Percent of a Number (4.3)
To find a percent of a number, you can use mental techniques like halving, doubling, and dividing by ten.

When calculating the percent of a number, convert the percent to a decimal, and multiply it by the number.

ex. 12 1/2% of 50 -> 0.125 x 50 = 6.25
12 1/2% of 50 = 6.25

Combining Percents (4.4)
To solve certain problems, percents can be added together to form one percent.

ex.
GST + PST = taxes
GST = 5% PST = 7%
taxes = 5% + 7%
taxes= 12%

There are two ways to calculate the increase of a number. They are:

a) Adding the combined percent value to the original number.

eg. 12% of 100 -> 0.12 x 100 = 12
12 + 100 = 112

b) Using a singel percent greater than 100, and multiplying that to the original number.

eg. 112% of 100 -> 1.12 x 100 = 112