Area of a triangle. Easy method of finding the area of a triangle in math.

To find the area of a triangle, multiply the base of the triangle by its perpendicular height (the vertical height), and divide your answer by 2. Basically, you do exactly the same as you would when finding the area of a rectangle, but you just half your final answer. This is because a rectangle can be split into two identical triangles.

You can also write this as a formula as A = bh/2 (b stands for the base length and h is the perpendicular height).

The most common mistake pupils make when finding the area of a triangle is that they forget to divide by 2.

Example 1

Find the area of this triangle.

Answer

First multiply the base of the triangle by the perpendicular height .

6 × 7 = 42

Now divide this answer by 2 (always remember to do this!)

42 ÷ 2 = 21 cm²

If you prefer you can always substitute your numbers directly into the formula (A=bh/2)

A = bh/2

A= 6 × 7 ÷ 2

A= 21 cm²

Example 2

Find the area of this triangle.

Answer

Again, you need to multiply the base of the triangle by its perpendicular height. Be careful not to use the sloping edge of 4cm, as it’s not the perpendicular height of the triangle.

8 × 5 = 40

Now, all you need to do next is to divide this answer by 2.

40 ÷ 2 = 20 cm²

or use the formula for finding the area of the triangle.

A = bh/2

A= 8 × 5 ÷ 2

A= 20 cm²