How do you find the area of a right triangle?

In this lesson you will learn how to find the area of a right

triangle by composing a rectangle.

Let’s ReviewLet’s Review

You find the area of a rectangle by multiplying length times width.

length

widt

h

Let’s ReviewA Common MistakeOnly finding the area of a rectangle and not

the triangle.

Let’s ReviewCore LessonA right triangle is half of a rectangle.

Let’s ReviewCore Lesson Let’s find the area of one of the sails.

length x width

4 units7

units

7x 428 units¤

2821 4units¤

Let’s ReviewCore Lesson

7 units5

units

7x 535 units¤17.5 units¤

2

In this lesson you have learned how to find the area of a right

triangle by composing a rectangle.

Let’s ReviewGuided PracticeFind the area of the right triangle.

21 units

8 un

its 21x 8168

84 units¤units¤

Let’s ReviewExtension Activities

Find an object in the classroom that is in the shape of a right triangle. Measure the sides to the nearest half inch. Then, using grid paper, find the area of the triangle using strategies from this video.

Let’s ReviewExtension Activities

Draw and then cut out 5 sets of congruent right triangles on grid paper. Tape each pair of congruent triangles together to form a rectangle. Label both the area of the rectangle and the area of each triangle on each set.

Let’s ReviewQuick Quiz

1. Find the area. 2. Find the area.