Perimeter and Area
Class 6 · Mathematics
5 ideas in Class 6 Mathematics, explained in plain words, with games and quizzes to practise.
Perimeter of Rectangles
Part of: Understanding Perimeter
The perimeter of a rectangle is the total distance around its edges. Imagine walking around a rectangular garden—the distance you walk is the perimeter. Since opposite sides of a rectangle are equal, you can calculate it quickly using length and breadth: perimeter = 2 × (length + breadth). A garden that is 8 metres long and 5 metres wide has a perimeter of 2 × (8 + 5) = 26 metres.
Why it matters. Perimeter helps you buy the right amount of fencing for a field, border for a picture frame, or tape to go around a table. Understanding this formula saves time when dealing with large measurements.
Try it in two minutes
- Draw a rectangle on paper with sides marked 7 cm and 4 cm.
- Ask your child: if you walk around it, do you walk 7 + 4 or do you walk each side? Walk around with a finger.
- Count: 7 + 4 + 7 + 4 = 22 cm. Then show the shortcut: 2 × (7 + 4) = 22 cm.
- Together, measure a real rectangular object at home (a book, a tile) and calculate its perimeter.
Try at home. Measure the length and breadth of a rectangular rug or door at home. Calculate its perimeter using the formula. Then check with a measuring tape by walking around the edges.
Perimeter of Squares
Part of: Understanding Perimeter
A square has four equal sides. Its perimeter is simply four times the length of one side. If each side is 5 cm, the perimeter is 4 × 5 = 20 cm. You can walk around a square room by going along four equal paths, one on each side.
Why it matters. Squares are common shapes in building designs, tiles and playground layouts. Knowing the perimeter helps you estimate how much border or fence you need.
Try it in two minutes
- Cut a square piece of paper with sides of 6 cm each.
- Ask: what is the perimeter if you go around once?
- Count the sides: 6 + 6 + 6 + 6 = 24 cm. Or use the shortcut: 4 × 6 = 24 cm.
- Draw more squares with different side lengths and calculate perimeters together.
Try at home. Find any square object at your home. Measure one side with a tape measure. Then measure the other three sides. Write down all four measurements and check if they are equal.
Perimeter of Triangles
Part of: Understanding Perimeter
A triangle has three sides. To find its perimeter, you simply add the lengths of all three sides. A triangle with sides 3 cm, 4 cm and 5 cm has a perimeter of 3 + 4 + 5 = 12 cm. An equilateral triangle has all three sides equal, so you can use the shortcut: perimeter = 3 × side.
Why it matters. Triangles appear in tent designs, roof shapes and warning signs. Knowing how to find the perimeter helps you calculate material needed for borders or edges.
Try it in two minutes
- Draw a triangle on paper with sides marked 5 cm, 6 cm and 7 cm.
- Ask: how far is it around this triangle? Go around with a finger.
- Add: 5 + 6 + 7 = 18 cm. That is the perimeter.
- Try an equilateral triangle (all sides equal) and show the shortcut: 3 × side.
Try at home. Cut out a triangle from cardboard. Measure all three sides and calculate the perimeter. Check by measuring around the triangle with a measuring tape.
Area of Rectangles and Squares
Part of: Understanding Area
Area is the amount of space covered by a flat shape. For a rectangle, multiply length by breadth. For a square, multiply side by side (since length equals breadth). A rectangular room that is 6 m long and 4 m wide covers an area of 6 × 4 = 24 square metres. Square tiles with sides 2 cm each cover 2 × 2 = 4 square centimetres.
Why it matters. Area helps you buy the right amount of paint for walls, tiles for a floor, or cloth for a tablecloth. It is useful whenever you need to measure surface space.
Try it in two minutes
- Draw a rectangle on squared paper with length 5 squares and breadth 3 squares.
- Count all the small squares inside. You get 15 squares.
- Show that 5 × 3 = 15 matches the count.
- Try a square with side 4 squares and count: 4 × 4 = 16 squares.
Try at home. Measure the length and breadth of a tile or a tabletop in your home. Calculate the area. Count or estimate how many of those tiles would cover your kitchen or bedroom floor.
Area of Triangles
Part of: Understanding Area
A triangle is half of a rectangle when the triangle is formed by cutting the rectangle along a diagonal. If you draw a rectangle and cut it diagonally, you get two triangles. So the area of one triangle is half the area of the rectangle. If a rectangle is 8 m long and 4 m wide (area 32 sq m), each triangle formed has area 16 sq m (half of 32).
Why it matters. Triangular shapes appear in roof designs, sails on boats and traffic signs. Understanding triangle areas helps you calculate materials needed for triangular spaces.
Try it in two minutes
- Cut a rectangular piece of paper. Measure and record the length and breadth.
- Draw a diagonal line from one corner to the opposite corner.
- Cut along the diagonal to get two triangles.
- Ask: if the rectangle's area is length × breadth, what do you think the triangle's area is? (Half of that.)
Try at home. Draw a rectangle on graph paper. Cut it diagonally. Count the small squares in one triangle and verify it is half the rectangle's squares.
What your child will practise
- Area of Rectangles and Squares: Number Quest (Collect the Answer)
- Area of Triangles: Candy Quick Fire (Quick Fire)
- Perimeter of Rectangles: Builder Sort (Sort It Out)
- Perimeter of Squares: Jungle Puzzle (Clue Puzzle)
- Perimeter of Triangles: Ocean Quick Fire (Quick Fire)
- Quiz: Area of Rectangles and Squares (8 questions)
- Quiz: Area of Triangles (8 questions)
- Quiz: Perimeter of Rectangles (8 questions)
- Quiz: Perimeter of Squares (8 questions)