A ratio is a comparison between two quantities. For example, in the picture below there are 5 butterflies for every 3 bees. The ratio of butterflies to bees can be written 3 ways
5:3
5 to 3
5 butterflies for every 3 bees
We will be looking at two types of ratios:
Part-to-PartRatios are the relationship between two distinct groups. For example, comparing strawberries to apples (comparing two different parts of the image). This ratio is 4:3.
Part-to-WholeRatios are the relationship between a group and the entire population. For example, comparing strawberries to all fruit (comparing one part of the image to the whole image).This ratio is 4:7.
Percentage:
Percent means “out of 100”
It is often written as %
It is a special ratio that compares to 100.
It is a part-to-whole ratio that compares a number to a whole divided into 100 equal parts.
For example, on a test you may get 87% right. This means that you had 87 out of 100!
In this unit, we are representing percentages in 4 ways:
Ratios
Fractions
Decimals
Percent
See the following example:
Finding the simplest fraction:
When looking for the simplest fraction, you must use division!
Find the largest number that is divisible by both numbers! If 100 can be divided by the numerator, use that! (example 1)
If 100 is not divisible by the numerator, try finding the largest number that can be divided into both! (example 2)
If you do not know the largest number that can be divided into both, choose a number that works! Keep dividing until your number cannot get any smaller! (example 3)
Easy calculations that will help with this chapter:
Here are some easy shortcuts to help you with the calculations in this unit!
Online Manipulatives
Check out some of these online manipulitaves to help you visualize ratios, percentages, decimals and fractions!