Learn the 3-Step Method
1Split into rectangles.
Draw a dashed line to cut the L into two rectangles.
2Find any missing sides.
Use the sides you know: whole width − part width, etc.
3Add the areas.
Area A + Area B = total area.
Worked Example
An L-shape: total width 10 cm, total height 10 cm. The top rectangle is 10 × 5; the bottom-right piece is 7 × 5. Find the total area.
Watch Out! Common Mistakes
Wrong! That fills in the notch. Split and add the real pieces: 85 cm².
Careful! An L-shape has 6 sides. Trace the outline with a finger and tick each side as you add it.
Don’t guess! Calculate: if the whole width is 10 and one part is 3, the other part is 10 − 3 = 7.
⬇ Cheat Sheet
- Split the shape into rectangles.
- Find missing sides by subtracting.
- Area: add the pieces' areas.
- Perimeter: trace and add ALL outside edges.
📖 Continue Your Journey
Quick summary
- Split compound shapes into rectangles with a dashed line.
- Find missing sides by subtracting known ones.
- Total area = sum of the rectangle areas.
- For perimeter, trace and add every outside edge — L-shapes have six.
Frequently asked questions
How do you find the area of an L-shape?
Split it into two rectangles, work out each area, then add them. Find any missing side lengths by subtracting known sides first.
How do you find a missing side on a compound shape?
Opposite edges must add up: if the total width is 10 cm and one part is 3 cm, the other part is 7 cm.
What's the most common compound-shape error?
Multiplying the two outer dimensions as if the shape were a full rectangle — which wrongly includes the missing notch.
Continue your child's learning journey
with the MindBlaze app.
Fun daily learning missions for children. Clear progress insights for parents — helping every child start secondary school ready to learn.
