Proportionality Review

Last week we began reviewing some topics that we have already covered but I feel we need another dose of before we take the 7th grade STAAR test on April 21st.  The first topic is proportionality.  This is one of the most helpful tools in mathematics.  We use proportions everywhere, in recipes, house plans, looking at student to professor ratios in colleges, baseball averages, etc.  We see proportions everywhere.

We began by reviewing how to determine if two ratios make a proportion.  If you find the cross products of the two ratios and they are equal your ratios make a proportion, if they don't they do not make a proportion.

ex.

Next, we looked at similar figures.  Similar figures have 4 characteristics that we must know:

1. They are the same shape,

2. They  are different sizes,

3. Their corresponding angles are congruent and,

4. Their corresponding sides are proportional.

With similar figures you have to be able to determine if 2 shapes are similar and if the shapes are similar find a missing part.

ex.

The third topic we discussed is the percent proportion.  You can use this proportion to solve almost every percent problem given.

  %   =   part  

100      total

There are 3 types of percent problems.  Problems where the part is missing, the total is missing, and the percent is missing.

Each one of these problems can be worked with the percent proportion.

The first problem sets up like this:

The second problem

The third problem