To be used with Lesson 9.5 Everyday Mathematics for Grade 5. How to find the are of non-rectangles.

1. Personal references
1cm
Everyday objects that give us an idea
about standard measurements.

2. Last time, you used TWO different
methods to find the area of a
rectangle. What were they?
Don’t panic!

3. Working by yourself or with a
partner, go through page 309.
Try out some different ways of finding
the area of non-rectangles.
Then, let’s chat about it!

4. What were some strategies that
worked?

5. Strategy 1: Add the parts!
1. Split into right triangles.
2. Turn it into a rectangle.
3. Find the area.
4. Divide by 2.
5. Add the parts!

6. Strategy 2: Subtract the Excess!
Sometimes, you can’t split a triangle into nice
right triangles. So we need another method.

7. Strategy 2: Subtract the Excess!
1. Make a rectangle around the whole
triangle.
2. Find the area of the parts.
3. Find the area of the green triangle:
use the strategy we just learned.
Draw a square.
Find the area.
Divide by 2.
4. Subtract the parts from the
whole!!

8. Strategy 2: Subtract the Excess! (for
parallelograms)
1. Make a rectangle around the whole
triangle.
2. Find the area of the parts.
3. Find the area of the blue and
green triangles: use the strategy we
just learned.
Draw a square.
Find the area.
Divide by 2.
4. Subtract the parts from the
whole!!

9. You try it!
Practice on page 310.
When you finish, check your work
with another student.
Then, play Frac-Tac-Toe!