Triangle Area Demonstration This resource provides animated demonstrations

Triangle – Area – Demonstration This resource provides animated demonstrations of the mathematical method. Check animations and delete slides not needed for your class.

(Hint: What is the total rectangular area? ) 2 cm 2 1 cm = 1 cm 2 1 cm Find the area of each shape. 1 cm 2 4 cm 2 3 cm 2 4. 5 cm 2

What is the area of this square? 4 cm If we cut the square into two: what is the new shape? what is the area of the new shape?

What is the area of this rectangle? 3 cm 6 cm If we cut the rectangle into two: what is the new shape? what is the area of the new shape?

We start with a rectangle… 4 cm 6 cm If we cut the rectangle into a triangle: what is the new shape? what is the area of the new shape?

We start with a rectangle… 4 cm Equal areas 6 cm If we cut the rectangle into a triangle: what is the new shape? what is the area of the new shape?

What is the area of each triangle? 6 cm 4 cm 6 cm 8 cm 4 cm 5 cm Area = 16 cm 2 Area = 12 cm 2 Area = 15 cm 2 What is the formula to find the area of any triangle? Area of a triangle = half × base × height Height Base

6 cm 10 cm Which method would you use? 10 × 6 then divide by 2 half the base then multiply by the height

6 cm 5 cm 4 cm What has Anne done wrong? We must use the perpendicular height from the base. The perpendicular height is at an angle of 90° from the base

Does the formula still work? 1) Doubling the triangle we make a parallelogram. 2) Area of a parallelogram = base × height 3) We want half that, so, half the base x height Height Base

Right or wrong? Would we use these measurements for base & height?

For each triangle, which measurements can we use for the base, and for the perpendicular height? 15 cm 2 7 cm 5 cm 16 4 cm cm 2 20 cm 2 7 cm 5 cm 10 cm 6 cm 8 cm 3 cm 10 cm 15 cm 2 Find the area of each triangle. 8 cm 4 cm 6 cm 11 cm 8 cm 10 cm 40 cm 2 4. 8 cm 10 cm 24 cm 2

Area of a triangle = half × base × height 4 cm = 4 cm 2

Area of a triangle = half × base × height 4 cm = 10 cm 2

Area of a triangle = half × base × height 7 cm 6 cm 5 cm = 15 cm 2

Area of a triangle = half × base × height 3 m 5 m 4 m = 6 m 2

Area of a triangle = half × base × height 7 cm 6 cm 8 cm = 24 cm 2

Area of a triangle = half × base × height 4 cm = 6 cm 2

Area of a triangle = half × base × height 6 m 7 m 5 m 10 m = 25 m 2

Area of a triangle = half × base × height 9 cm 6 cm 8 cm = 27 cm 2

Area of a triangle = half × base × height 8 cm = 32 cm 2

Area of a triangle = half × base × height 15 cm 12 cm 4 cm 6 cm = 30 cm 2

Area of a triangle = half × base × height 14 cm 8 cm 12 cm = 48 cm 2

Questions? Comments? Suggestions? …or have you found a mistake!? Any feedback would be appreciated . Please feel free to email: tom@goteachmaths. co. uk