NCERT Ganita Prakash, Class 7, textbook pages 1–23 (Part 2)

How to teach Class 7 Maths Part 2 Chapter 1, Geometric Twins, at home

Congruent figures and congruence of triangles, taught with things you already have at home: a 20-minute activity, a game for the week, a 5-day plan and the mistakes to watch for.

△ABC ≅ △PQR

NCERT Class 7 Maths Part 2 Chapter 1 Geometric Twins: what it teaches

Two figures are congruent (geometric twins) if one fits exactly on the other. Your child checks congruence by tracing, learns the conditions SSS, SAS, ASA/AAS and RHS for triangles, and sees why SSA doesn’t always work.

Why it matters later. Congruence is the basis of geometric proof in Classes 9 and 10.

See it: this chapter in pictures

SSS SAS ASA RHSenough to prove congruenceAAA and SSA are not
Four rules guarantee twins.
same angles, different size: not congruent
AAA gives the same shape, not the same size.
△ABC ≅ △PQRA↔P B↔Q C↔RAB = PQ, ∠B = ∠Q …
Order of letters matters.

You need

  • tracing paper
  • ruler, compass, protractor
  • scissors

Tonight’s 20 minutes

  1. Trace a shape and check if it fits another exactly (you may flip it).
  2. Construct two triangles with sides 4, 5, 6 cm. Are they congruent?
  3. Construct triangles with two sides and the included angle. Congruent?
  4. Try two sides and a non-included angle: can you make two different triangles?

Words to use

  • congruent
  • corresponding parts
  • SSS
  • SAS
  • ASA
  • RHS

Watch for

  • Matching the wrong corresponding parts. Name vertices in order: △ABC ≅ △PQR means A↔P, B↔Q, C↔R.
  • Using SSA as a rule. Show two different triangles with the same SSA data.

What it sounds like at home

A short example of the conversation. Your words will differ; the questions are what matter.

YouTwo sides and the angle between them match. Congruent?

Your childYes, SAS.

A game for this week: Twin or not?

  1. Draw pairs of triangles with some measurements given.
  2. The other player says congruent or not, naming the rule.
  3. Check by tracing.
  4. One point per correct rule.

A 5-day plan, 20 minutes a day

  1. Day 1Tracing test.
  2. Day 2SSS construction.
  3. Day 3SAS construction.
  4. Day 4Why SSA fails.
  5. Day 5Twin or not? game.

Everyday moments to practise

  • Tiles of the same size.
  • Mass-produced parts.
  • Paper cut-outs.
  • Bridge trusses.

Quick check

Ask these at the end of the week. Tap to see the answer.

Are all equilateral triangles with side 5 cm congruent?

Yes (SSS).

Is AAA enough for congruence?

No, triangles can be the same shape but different sizes.

Which rule uses a right angle, hypotenuse and a side?

RHS.

Ready for the next chapter when your child…

  • Checks congruence by superposition.
  • Names SSS, SAS, ASA, RHS.
  • Matches corresponding parts.

Activities, wording and illustrations are Mathify Kids’ own, following the topics of NCERT’s Ganita Prakash (Class 7). See the full Class 7 parent guide for every chapter.

Questions parents ask

What does congruent mean?

Same shape and same size.

Why isn’t AAA a congruence rule?

It only guarantees same shape, not size.

What is the included angle?

The angle between the two given sides.