NCERT Ganita Prakash, Class 8, textbook pages 135–147 (Part 2)

How to teach Class 8 Maths Part 2 Chapter 6, Algebra Play, at home

Puzzles and tricks explained with algebra, taught with things you already have at home: a 30-minute activity, a game for the week, a 5-day plan and the mistakes to watch for.

think of n(2n + 10) ÷ 2 − n= 5, always

NCERT Class 8 Maths Part 2 Chapter 6 Algebra Play: what it teaches

Number tricks and puzzles become clear with algebra. Your child builds and explains think-of-a-number tricks, calendar tricks and digit puzzles by writing them as expressions.

Why it matters later. Algebraic reasoning is the main tool of Classes 9–12 mathematics.

See it: this chapter in pictures

3 × 3 calendar boxsum = 9 × middle datemiddle 15 → 135
Algebra explains the calendar trick.
73 − 37 = 36(10a + b) − (10b + a)= 9(a − b)
Always a multiple of 9.
invent a trickwrite it with nshow n cancels out
Make n disappear.

You need

  • paper and pencil
  • a calendar

Tonight’s 30 minutes

  1. Trick: think of a number, double it, add 10, halve, subtract the number. Always 5. Why? (Use n.)
  2. Calendar: pick a 3 × 3 box of dates; the sum is 9 × the middle date. Prove it.
  3. Reverse a two-digit number and subtract: always a multiple of 9. Why?
  4. Invent your own trick and explain it with algebra.

Words to use

  • expression
  • variable
  • prove
  • simplify
  • trick

Watch for

  • Checking with one number only. Use a letter to show it works for all numbers.
  • Errors simplifying. Write each step on a new line.

What it sounds like at home

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

YouWhy is it always 5?

Your child(2n + 10) ÷ 2 − n = 5.

A game for this week: Trick maker

  1. Invent a think-of-a-number trick.
  2. Try it on family.
  3. Explain with algebra.
  4. Best trick wins.

A 5-day plan, 30 minutes a day

  1. Day 1Think-of-a-number trick.
  2. Day 2Calendar box sums.
  3. Day 3Digit reversal.
  4. Day 4Invent a trick.
  5. Day 5Trick maker game.

Everyday moments to practise

  • Magic tricks at parties.
  • Calendar puzzles.
  • Number riddles.
  • Mental maths games.

Quick check

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

Double, add 10, halve, subtract n: result?

5.

Sum of 3 × 3 calendar box with middle 15?

135.

73 − 37?

36, a multiple of 9.

Ready for the next chapter when your child…

  • Explains tricks with algebra.
  • Simplifies expressions accurately.
  • Creates own puzzles.

Activities, wording and illustrations are Mathify Kids’ own, following the topics of NCERT’s Ganita Prakash (Class 8). See the full Class 8 parent guide for every chapter.

Questions parents ask

How does algebra explain tricks?

Writing the steps with n shows the result doesn’t depend on n.

Why is a reversed-digit difference a multiple of 9?

(10a + b) − (10b + a) = 9(a − b).

Is this chapter tested?

It develops reasoning; exercises check explanations.