11+ Maths: Compound Shape Perimeter Practice (CEM & GL)
21 October 2026
Why practise compound shape perimeters
Understanding how to find the perimeter of compound shapes is a key skill for 11+ Maths. These questions often appear in both CEM and GL exams. Practising helps children spot all the sides that make up the outer edge of these shapes.
What is a compound shape
A compound shape is made by joining two or more simple shapes, such as rectangles or squares. To find the perimeter, you need to add up the lengths of all the outer sides, taking care not to count any shared lines twice.
Worked example
Imagine an L-shaped figure made from two rectangles.
The first rectangle is 5 cm by 3 cm. The second rectangle is 2 cm by 4 cm and is joined to the first to make an L-shape.
Step 1: Draw the shape and label all the sides. Some sides are shared between the two rectangles.
Step 2: List all the sides that form the outside edge. For this shape, the outer sides are 5 cm, 3 cm, 2 cm, 1 cm, 4 cm, and 6 cm.
Step 3: Add up these lengths: 5 + 3 + 2 + 1 + 4 + 6 = 21
The total perimeter is 21 cm.
Tips for helping your child
Encourage your child to trace the outline of the shape with a finger or pencil, so they only count each outside edge once. Remind them to look out for sides that are not part of the perimeter because they are inside the shape.
Key insight: Practising with compound shapes builds confidence in recognising which sides to add and helps avoid common mistakes in perimeter questions.
For more practice
You can find targeted worksheets and interactive questions on the 11+ Maths: Compound Shape Perimeter Practice (CEM & GL) page.
