Area of Triangles
This topic covers 4 learning steps, guiding your child from the basics through to confident problem-solving. Each step includes a worked example and adaptive practice questions.
What Your Child Will Learn
- Half a Rectangle
Understand a triangle as half of a rectangle - The Formula
Use A = base x height / 2 - Find Missing Measurements
Given area and one measurement, find the other - Challenge — Combined Triangle Problems
Multi-step triangle area problems
Common Mistakes
- Using base × height without halving (giving double the actual area)
A triangle is exactly HALF of a rectangle with the same base and height. So the formula is (base × height) ÷ 2. Draw a rectangle around the triangle to prove it — the triangle takes up exactly half the space. - Using the slanted side instead of the perpendicular height
The "height" in the formula must be the PERPENDICULAR (vertical) distance from the base to the opposite point — not the slanted side. Draw a dashed line straight down from the top to the base.
Tips for Parents
- Cut a rectangle from paper, then cut it diagonally to make two triangles. Each triangle is half the rectangle — proving the formula.
- Find triangular shapes around the house (road signs, coat hangers, sandwich halves) and discuss how you would measure their base and height.
- Draw triangles on squared paper and work out the area by counting squares (full squares + half squares), then verify with the formula.
- Ask: "A triangle has a base of 6 cm and a height of 4 cm. What is the area?" Then: "What if I double the base?" (Area doubles too.)
Key Words
- Base — The bottom side of a triangle — the side you measure the height from.
- Height (perpendicular) — The straight-down distance from the base to the top point of the triangle.
- Area of a triangle — The space inside a triangle — calculated as (base × height) ÷ 2.
- Perpendicular — At a right angle (90°) to something — the height must be perpendicular to the base.
Where This Fits
Before this topic: Children should know the area formula for rectangles and understand what area measures.
After this topic: The area of triangles leads to areas of other shapes (parallelograms, trapeziums), composite area problems, and trigonometry in secondary school.
How MathCraft Teaches This
In MathCraft, Area of Triangles is taught through the Geometry & Shape adventure track. Your child follows guided lessons with friendly characters, works through examples step by step, then practises with questions that adapt to their level.
The adaptive engine tracks mastery across all 4 steps, revisiting concepts your child finds tricky and advancing when they're ready. Parents can see detailed progress in the Parent Dashboard.
Practise Area of Triangles with MathCraft
Step-by-step lessons, worked examples, and adaptive practice — all wrapped in an adventure game your child will love.
Try MathCraft Free No credit card required