Worked example
27 October 2026
Triangles on a grid can look tricky, but with the right approach, your child can understand how to work out both area and perimeter. By using the measurements given on the grid, you can break down each part of the problem into simple steps.
Worked example
A triangle is drawn on a grid. The base is 4 squares long. The height is 3 squares tall.
Step 1: Find the area.
Area of a triangle = (base × height) ÷ 2
Base = 4
Height = 3
4 × 3 = 12
12 ÷ 2 = 6
The area is 6 square units.
Step 2: Find the perimeter.
The triangle has sides of 4 units, 3 units, and 5 units (the third side is the diagonal, which is 5 units long).
Perimeter = 4 + 3 + 5 = 12 units
The correct answers are: area = 6 square units, perimeter = 12 units.
After working through this example, your child will know how to spot the base and height of a triangle on a grid, and how to add up the side lengths for the perimeter. This is the same method they can use when practising similar questions on area and perimeter of triangles in their 11+ maths preparation.
