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CBSE Class 4 · Mathematics

The Cleanest Village

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 “The Cleanest Village” 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 Shillong field-trip poster is a counted plan

A poster that lists houses or children is a plan only after each list is a count. A pretty hill drawing is not the plan.

“Many houses” is not a numeral.

Figure. A Shillong field-trip poster is a counted plan: 12 houses plus 18 houses is 30, a number near 30 you can point at.

How it works

  1. Name the pileHouses, or children.
  2. Count one-to-oneLast word is the size.
  3. Write the numeral on the posterThat is the plan’s number.

2Join groups of children or houses

Children already counted plus children who join is a join. Write plus only after you can say they joined.

Two villages that never meet are not a join.

Figure. In 25 the digit 2 sits in the tens house and names 20, not 2. Rebuild 20 plus 5.

How it works

  1. Count group AStart.
  2. Count group BThe joining group.
  3. AddThat sum is how many now.

3A clean village is a data story later; here it is a count

Cleanliness as a table of bins waits for data-handling. This chapter’s job is the count of people, houses, or bags.

Do not skip the count to write a slogan.

Figure. Each tally is one observation. Five equal marks still count five; the height of the count bar is the same five.

How it works

  1. Pick what you will countHouses, or bags.
  2. Finish that countA numeral.
  3. Leave “cleanest” as the settingNot a substitute number.

4Add two-digit or three-digit groups

148 + 76: ones, then tens, then hundreds. Line the houses up.

Adding 148 + 76 as 14876 is a mash, not a join.

Figure. Join two two-digit groups by houses: 42 is 4 tens and 2 ones, 25 is 2 tens and 5 ones, total 67.

How it works

  1. Line up ones8 under 6.
  2. Add ones, then tens, then hundredsCarry if a house passes 9.
  3. Write the sumOne numeral.

Join two village counts

One lane has 148 houses. Another has 76. How many houses together?

  • Ones8 + 6 = 14 → 4 ones, 1 ten
  • Tens4 + 7 + 1 = 12 → 2 tens, 1 hundred
  • Hundreds1 + 1 = 2
  • Sum224

Pro tip. Houses lined up. A carry is a trade, not a new village.

5Regroup tens as hundreds when needed

Ten tens trade for one hundred. Writing 14 in the tens house is an unfinished trade.

The village total stays the same; only the houses change.

Figure. Ten tens regroup as one hundred. Adding 84 and 26 fills 10 ones and 11 tens, written as 110.

How it works

  1. Add tensSee 10 or more.
  2. Trade 10 tens → 1 hundredCarry.
  3. Leave leftover tens0 to 9.

6Estimate first

148 + 76 is near 150 + 80 = 230. Estimate by nearby tens or hundreds, then compute exactly.

The estimate is a neighbour, not a replacement if you need exact.

Figure. Estimate first: 38 and 44 both sit near 40 on the line, so 38 + 44 is about 80 before you add exactly.

How it works

  1. Round each addend148 → 150, 76 → 80.
  2. Add thoseA neighbour.
  3. Then compute exactlyCheck you are close.

7Check by the opposite action

After 148 + 76 = 224, check 224 − 76 = 148. The opposite must rebuild a start.

A check that starts a new poster is not a check.

Figure. Check a join by the opposite take-away: 36 + 28 = 64 is true only if 64 minus 28 returns 36.

How it works

  1. Keep the result224.
  2. Do the oppositeSubtract one addend.
  3. Demand a start148, or redo.

8The poster is the story; the arithmetic is the join

Shillong is the picture. Plus and carry are ordinary joins.

Do not invent a hill-only plus.

Figure. The poster is the story; the arithmetic is the join. 16 beads and 14 more make 30, the same total you can count.

How it works

  1. Name the numbersSizes of groups.
  2. Name the storyJoin.
  3. Use ordinary +The poster is not a new rule.
148 + 76 needs a tens-to-hundreds carry when
  1. Tens make 10 or more
  2. The poster is pretty
  3. Ones are 0

Ten tens trade for one hundred.

Notes

  • The official chapter title is “The Cleanest Village”. 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

  • Join: A + B = total.
  • Check: total - B = A.
  • If tens \ge 10, write tens - 10 and carry 1 hundred.

Recap

Hold these pegs from the official chapter “The Cleanest Village”. The wording is ExamMaster’s teaching, not a textbook recap.

A Shillong field-trip poster is a counted plan
A poster that lists houses or children is a plan only after each list is a count.
Join groups of children or houses
Children already counted plus children who join is a join.
A clean village is a data story later; here it is a count
Cleanliness as a table of bins waits for data-handling.
Add two-digit or three-digit groups
148 + 76: ones, then tens, then hundreds. Line the houses up.
Regroup tens as hundreds when needed
Ten tens trade for one hundred. Writing 14 in the tens house is an unfinished trade.
Estimate first
148 + 76 is near 150 + 80 = 230. Estimate by nearby tens or hundreds, then compute exactly.

Practise The Cleanest Village

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