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CBSE Class 4 · Mathematics

Elephants, Tigers, and Leopards

Official NCERT chapter from Math-Mela (book code demm1). ExamMaster notes are original teaching at CBSE Class 4 depth.

This lesson follows the official chapter “Elephants, Tigers, and Leopards” in Math-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 4
  • Easy level
  • 8 concepts

1A NIM pile is a count you take from

A pile of tokens is a start count. A turn takes some tokens away. The pile after the turn is a new count.

The animal names on the tokens are costumes. The count is the maths.

Figure. A NIM pile is one counted heap you take from. Seven tokens is the count. The pile is the object, not a picture of an animal.

How it works

  1. Count the pileStart size.
  2. Name a takeA counted part.
  3. Write the leftoverStart − take.

3The leftover pile is a subtraction

Start 18, take 3, leftover 15. Every legal take is minus.

Do not add because the animal token looks friendly.

Figure. The leftover pile is a subtraction. After a take of 2 from 7, five tokens remain: 7 − 2 = 5. The leftover is still one pile, not a new game.

How it works

  1. Write start18.
  2. Write take3.
  3. Subtract15.

One take from a pile

A pile has 18 tokens. A player takes 3 (allowed). What is left?

  • Start18
  • Take3
  • Leftover18 − 3 = 15

Pro tip. A legal take is subtraction. Check: 15 + 3 = 18.

4Two players share one running total

After A takes, B faces the leftover, not a fresh pile. The running total is one number both must trust.

Secretly resetting the pile is not this game.

Figure. Two players share one running pile. The count does not reset on a turn change. Player A and Player B take from the same five tokens.

How it works

  1. Record the leftoverThe new total.
  2. Hand that number to the next playerSame pile.
  3. Each turn subtracts from that running totalOne story.

5A strategy is a plan; the arithmetic is still take-away

A plan might say “leave a multiple of 4”. The move is still a subtraction you can check.

A clever plan that miscounts the leftover is a broken plan.

Figure. A strategy is a plan for what to leave. The arithmetic is still take-away: 6 − 2 = 4. The plan does not replace the subtraction.

How it works

  1. Say the plan if you have oneLeave 4, 8, 12, …
  2. Compute the takeStart − target.
  3. Check the leftover is the targetArithmetic first.

6Equal groups can hide inside a long game

If every turn takes 2, the landings are a skip-count. Equal groups hide in the running total.

Turns of mixed legal sizes are not one equal-group story unless you say so.

Figure. Equal groups can hide inside a long game. Three rows of four tokens is the array 3 × 4 = 12. If the groups are not equal, it is not multiplication yet.

How it works

  1. See if takes are the same sizeAlways 2?
  2. If yes, skip-count18, 16, 14, …
  3. If mixed, subtract each turn on its ownNo fake array.

7Zero on the pile is the empty count

A pile of 0 is empty. Taking from 0 is not a legal take. The player who faces 0 cannot take.

Empty is a size, not a skip of the game record.

Figure. Zero on the pile is the empty count. Three tokens is a pile of 3. An empty box is 0 — not a missing number, and not a new animal.

How it works

  1. See 0No token to point to.
  2. Refuse a takeNothing to subtract.
  3. Record emptyZero is the numeral.

8The animals name the tokens; the move is the maths

Elephant, tiger, leopard can label tokens or players. The move is still a counted take-away.

Do not invent a special animal-plus.

Figure. Elephant, tiger, and leopard name the tokens. The move is still a counted take. Here the take is 2 — the animal names do not change the subtraction.

How it works

  1. Keep the costumeA name on a token.
  2. Count the takeA number.
  3. Subtract from the running totalThe maths.
Start 18, legal take 3. Leftover is
  1. 15
  2. 21
  3. 18

A take is minus.

Notes

  • The official chapter title is “Elephants, Tigers, and Leopards”. 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.

Formulas

  • Leftover = start - legal take.
  • Check: leftover + take = start.

Recap

Hold these pegs from the official chapter “Elephants, Tigers, and Leopards”. The wording is ExamMaster’s teaching, not a textbook recap.

A NIM pile is a count you take from
A pile of tokens is a start count. A turn takes some tokens away. The pile after the turn is a new count.
A legal take is a counted part, not a random grab
A rule might allow 1, 2, or 3 tokens. A grab of 7 when 3 is the max is not a legal take.
The leftover pile is a subtraction
Start 18, take 3, leftover 15. Every legal take is minus.
Two players share one running total
After A takes, B faces the leftover, not a fresh pile.
A strategy is a plan; the arithmetic is still take-away
A plan might say “leave a multiple of 4”. The move is still a subtraction you can check.
Equal groups can hide inside a long game
If every turn takes 2, the landings are a skip-count.

Practise Elephants, Tigers, and Leopards

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