CBSE Class 3 · Mathematics
Fun with Shapes
Official NCERT chapter from Maths Mela (book code cemm1). ExamMaster notes are original teaching at CBSE Class 3 depth.
This lesson follows the official chapter “Fun with Shapes” in Maths Mela. The words below are ExamMaster’s teaching, not a paste from the book. Use the NCERT chapter for the classroom sequence; use these notes to hold the idea without copying exercises or figures.
- CBSE Class 3
- Easy level
- 8 concepts
1A rangoli is a pattern on a dotted grid
Dots that you can count are the grid. The rangoli copies a unit across those dots.
A free scribble with no repeating unit is a drawing, not this pattern.
Figure. A rangoli lives on countable dots. The same diamond unit is copied onto the next four dots. A free scribble with no repeating unit is just a drawing.
How it works
- See the dotsThey sit in rows.
- Find the unitThe bit that repeats.
- Copy it to the next dotsThat is the pattern.
2Dots that line up make a straight side
A straight side is dots you can cover with a stick. A wobble that misses the dots is not that side.
Count the sides only after each side is a straight join.
Figure. A straight side is a stick that covers every dot on that join. A wobble that misses the dots is not a side, so do not count it yet.
How it works
- Pick two dotsThe ends of a side.
- Check they line up with the ones betweenA stick would cover them.
- That join is one sideName it before the next.
3Closed shapes keep an inside
A closed path comes back to the start and keeps an inside. An open path leaks.
Colouring “inside” an open path is a pretend inside.
Figure. A closed path comes back to its start and keeps an inside you can point to. An open path has a gap, so colouring a pretend inside is a miss.
How it works
- Trace the pathDo you return?
- If yes, name the insideThe region it keeps.
- If no, it is openNo honest inside.
4Triangle, square, and rectangle by sides and corners
Three straight sides and three corners: triangle. Four equal sides and four square corners: square. Opposite sides equal, square corners: rectangle.
A pretty colour does not change the side-count.
Figure. Name the shape by a test, not by colour. Three straight sides: triangle. Four equal sides and square corners: square. Opposite sides equal and square corners: rectangle.
How it works
- Count straight sides3 or 4.
- Check cornersSquare, or not.
- Name by that testNot by colour.
5Same shape, different size
A small square and a large square share the side-test. Size changed; the name did not.
Do not call the large one a “new shape” only because it is bigger.
Figure. A small square and a large square share the side-and-corner test. The large one is drawn twice as wide and twice as tall. Size changed; the school name did not.
How it works
- Run the side-and-corner testSame name?
- Allow a new sizeBigger or smaller.
- Keep the school nameSquare stays square.
6A turn of the rangoli is not a new shape if it matches
Turn the unit and see if it sits on the same dots. If it matches, it is the same shape in a new facing.
A turn that needs extra dots is a different unit.
Figure. Turn the same right triangle a quarter-turn. The legs still meet square and still match in length, so it is the same shape in a new facing, not a new school name.
How it works
- Copy the unitOn tracing or in mind.
- Turn itQuarter or half.
- Ask if the dots still fitMatch means same shape.
7Copy the unit onto a new row to check
The next row must use the same unit. If you invent a new doodle, the pattern broke.
Checking is copying, not admiring.
Figure. The next row must reuse the same unit on the next dots. Checking is copying. If the second row invents a new doodle, the pattern broke.
How it works
- Hold the unitThe first row’s bit.
- Place it on the next row’s dotsSame size, same joins.
- If it fails, fix the copyDo not rename the failure a style.
8Almost even fails the fold later — here, count sides
“Looks like a square” is not four equal sides. Count and compare sides now; fold-tests can wait for a later chapter.
Almost is a miss.
Figure. Looks-like is not the test. Four equal sides and square corners make a square. A 3-by-4 rectangle can sit next to it and still fail that test.
How it works
- Count four sidesOr you do not have a quadrilateral.
- Compare lengthsEqual, or not.
- Name only what the test allowsRectangle, or just four-sided.
A path that does not return to the start has
- No honest inside
- A triangle inside
- Four square corners
An open path leaks. Closed shapes keep an inside.
Notes
- The official chapter title is “Fun with Shapes”. Teach the school test for that title, not a contest shortcut.
- If a step needs a later class, stop. The next official chapter will pick it up.
Recap
Hold these pegs from the official chapter “Fun with Shapes”. The wording is ExamMaster’s teaching, not a textbook recap.
- A rangoli is a pattern on a dotted grid
- Dots that you can count are the grid. The rangoli copies a unit across those dots.
- Dots that line up make a straight side
- A straight side is dots you can cover with a stick.
- Closed shapes keep an inside
- A closed path comes back to the start and keeps an inside.
- Triangle, square, and rectangle by sides and corners
- Three straight sides and three corners: triangle.
- Same shape, different size
- A small square and a large square share the side-test.
- A turn of the rangoli is not a new shape if it matches
- Turn the unit and see if it sits on the same dots.
Practise Fun with Shapes
Reading is free and needs no account. Practice, mocks and progress live in the app.
- A 4-question practice set that ends the chapter
- 1 quick check with worked explanations
- Timed mocks scored with the real marking scheme
- Readiness tracked per topic, kept on your device