How Big Is My Triangle?

How Big Is My Triangle?

Calculating the Area of a Triangle

A triangle is one-half of a parallelogram.The second triangle has been turned upside down.

When the second triangle is placed adjacent to the first one, the two triangles form a parallelogram.

1st triangle

2nd triangle

You know how to find the area of a parallelogram.

Base (b) = 6 in

Height (h) = 4 in

Base × Height (b × h) = Area6 × 4 = 24 square inches

If a triangle is half of a parallelogram, how do you think you find the area of a triangle?

Multiply base by height (b × h)

Multiply base by height and divide by 2(b × h) ÷ 2

Multiply base by height and multiply by 2b × h × 2

So, how do you find the base and height of a triangle?

A right triangle is easy

This isosceles triangle isn’t too hard

This scalene triangle can be a little more challenging

height

base

base

height

height

base

What is the area of the triangle below?

Use the formula (b × h) ÷ 215 square inches

10 square inches

7½ square inches3 in

5 in

Yes

No

Is the area of this triangle 8 square inches?

4 inches

4 inches

Draw lines to show where you could measure the base and height of this triangle.

If this triangle has the specified base and height, what is its area?

21 square inches

42 square inches

13½ squareinches

6 in

7 in

Draw lines to show where you could measure the base and height of this triangle.

If this triangle has the specified base and height, what is its area?

4½ square inches

18 square inches

9 square inches

9 in2 in