1) Lesson Objectives:

You should be able to 

• Know the relationship of similar figures

• Know how to find scale factors 

• Find the lengths of similar figures

Big Idea:

• Invariance is a property of a mathematical object which remains unchanged when the object undergoes some form of transformation. In geometry, the area of a figure, the angles within it, and the ratio of the sides remain unchanged when the figure is translated, reflected or rotated.  

• Proportionality is a relationship between two quantities that allows one quantity to be computed from the other based on multiplicative reasoning. 

Success Criteria:

I am able to 

• find scale factor of any given two figures.

• interpret what the scale factor means.

• rewrite a given scale to the form 1 : n.

• solve length questions on map scale.

• find the area scale from the length scale.

• solve area questions on map scale.

Always look through all examples in textbook before lesson.

Enlargement of Scale Factors 

In Similar Figure, Enlargement means there is a change in the size of the figure proportionally by a scale factor.

Scale factor is the ratio of the corresponding sides of the to figures.

When comparing scale factors of all corresponding sides, you must always use the same ratio.

Example of correct way of solving length of similar figures.

Example of incorrect way of solving length of similar figures.  

The ratio will not be equal when we use the different figures as numerator and denominator.

THIS IS NOT SUPPOSE TO BE EQUAL TO EACH OTHER.

Map Scale

The following document is a visual representation for conversion of Length and Area.  (Volume is additional for your knowledge only)

Prior Knowledge 

Solving Map Scale word problems.

Expressing map scale in the form 1 : n

Finding area in Map Scale