Hello, young mathematician! In this guide, we will use a school-trip setting to practise addition, subtraction, estimates, change, and number puzzles. The official NCERT chapter gives the scope; every explanation, example, activity, and question here is freshly written for PrincipalSaab.
Caregiver: Ask the child to say what each number means before they start calculating.
This guide follows Chapter 7, The Cleanest Village, from NCERT’s Maths Mela for Class 4 Mathematics. The chapter works with trip information, rupee amounts, totals, balances, regrouping, and playful number reasoning.
Words to Know
| Word | Simple meaning | Example |
|---|---|---|
| Total | the amount after joining groups | children in two buses |
| Balance | money left or money returned | change after buying |
| Estimate | a near answer used for checking | about 500 |
| Regroup | exchange 10 smaller units for 1 larger unit, or the reverse | 10 ones become 1 ten |
| Difference | how much more or less | 83 is 37 more than 46 |
Make a pretend class-trip shop with paper slips marked Rs 20, Rs 50, Rs 100, and Rs 500. Pick three safe household items, give each a price below Rs 200, then practise paying and returning exact change. (15-20 min)
Your Learning Plan
- Underline the quantities and rupee amounts.
- Decide whether the question asks for a total, a difference, or change.
- Estimate before exact calculation.
- Align ones, tens, and hundreds carefully.
- Check by reversing the operation where possible.
Keep a two-column rough-work habit. In the first column, write what the story is asking. In the second column, write the number sentence. This stops the working from becoming a loose pile of digits.
For this chapter, your best friends are labels. Write Rs for money, children for people, and items for objects. A label can reveal mistakes that a plain number hides.
Read The Story Numbers
Many Class 4 questions hide the operation inside a small story. Do not jump to a keyword. First ask: are two groups joining, is one group being taken away, or is a payment being compared with a cost?
In a trip story, numbers may describe people, distance, time, price, or change. Each number should keep its label. If the question asks for money, the answer needs rupees. If the question asks for children, the answer needs children.
A neat habit is to write a tiny note before calculating. For example, write children + children, paid – cost, or larger group – smaller group. This note is not extra decoration; it protects you from choosing the wrong operation.
Also watch for numbers that are only background information. A story may mention time, place, or distance, but the question may ask only about cost. Use the numbers that answer the question, and leave the others alone.
- A bus has 236 learners.
- Another bus has 187 learners.
- Add ones: 6 + 7 = 13, so write 3 ones and regroup 1 ten.
- Add tens: 3 + 8 + 1 = 12 tens, so write 2 tens and regroup 1 hundred.
- Add hundreds: 2 + 1 + 1 = 4 hundreds.
Answer: 236 + 187 = 423 learners.
Add With Regrouping
When we add numbers, ones join ones, tens join tens, and hundreds join hundreds. If 10 or more ones are formed, regroup 10 ones as 1 ten. If 10 or more tens are formed, regroup 10 tens as 1 hundred.
Column addition is neat only when place values are aligned. A one-digit number still belongs in the ones column. A two-digit number has tens and ones. A three-digit number has hundreds, tens, and ones.
Say the regrouping aloud while practising: “13 ones are 1 ten and 3 ones.” This sentence helps you understand the small 1 written above the tens column. It is not a magic mark; it is a ten that came from the ones.
For three-digit addition, there can be regrouping twice. First the ones may create a new ten. Then the tens may create a new hundred. Work from right to left and do not skip the checking sentence.
- Round 248 to about 250.
- Round 396 to about 400.
- Add 250 + 400.
Answer: The estimate is about 650.
After exact addition, compare the answer with your estimate. If the exact answer is far from the estimate, reread the numbers before moving on.
Estimate First
Estimating is not guessing lazily. It is a quick reasonableness check. For Class 4, rounding to the nearest ten or hundred is often enough. The estimate tells you the rough size of the answer.
If an exact answer to 248 + 396 is written as 164, the estimate catches the problem quickly because 250 + 400 is about 650. The exact answer should be near 650, not near 160.
Choose the estimate that fits the numbers. For 38 + 16, nearest tens are useful: 40 + 20 = about 60. For 438 + 476, nearest hundreds or friendly tens may be better: about 400 + 500 = about 900, or 440 + 480 = about 920.
An estimate does not need to equal the exact answer. Its job is to tell you whether the exact answer lives in the right neighbourhood.
- A notebook set costs Rs 176.
- The buyer pays Rs 200.
- Subtract 200 – 176.
Answer: The change is Rs 24.
Find Balance And Change
Balance and change problems compare what was paid with what was spent. If the buyer pays more than the cost, subtract the cost from the amount paid. The result is the money returned.
You can check change by adding back: cost + change = amount paid. This is one of the strongest checks in money questions.
Sometimes the question gives two of the three parts: paid amount, cost, and change. If you know paid amount and cost, subtract to find change. If you know paid amount and change, subtract to find cost. If you know cost and change, add them to find the paid amount.
Use play money or quick drawings when the subtraction feels heavy. Five hundreds, ten tens, and ten ones are not separate tricks; they are pictures of the same place-value idea.
- A display has 503 stickers.
- 268 stickers are used.
- Regroup 1 hundred as 10 tens, then 1 ten as 10 ones.
- 13 ones – 8 ones = 5 ones.
- 9 tens – 6 tens = 3 tens; 4 hundreds – 2 hundreds = 2 hundreds.
Answer: 503 – 268 = 235 stickers left.
- A library shelf has 184 storybooks.
- It has 57 more picture books than storybooks.
- Picture books = 184 + 57.
- Add with regrouping.
Answer: There are 241 picture books.
When a question gives the paid amount and the balance, the cost is also found by subtraction: cost = paid amount – balance. Keep the rupee symbol in the final sentence.
Subtract With Regrouping
Subtraction with regrouping is needed when the upper digit is smaller than the lower digit in a place. We exchange from the next place value, then subtract.
For example, in 503 – 268, there are not enough ones and not enough tens at first. Regrouping changes the same total into a form that can be subtracted place by place.
Zeros need special care. In 704 – 389, the ones column has 4 ones, so it cannot give away 9 ones. The tens column has 0 tens, so it cannot lend directly. We regroup 1 hundred into 10 tens, then regroup 1 ten into 10 ones. Now the number is still 704, but it is written in a form we can use.
After subtracting, add the difference back to the smaller number. If it returns to the larger number, your subtraction is steady.
- A puzzle side must total 21.
- Two numbers on the side are 9 and 5.
- Find the missing number: 21 – 9 – 5.
- 21 – 9 = 12 and 12 – 5 = 7.
Answer: The missing number is 7.
Solve Number Puzzles
Number puzzles train careful checking. In a side-sum puzzle, the same target must be reached in every side or row. The best method is to test, adjust, and check all conditions.
Do not use a number twice unless the rule allows it. Do not leave a number unused when the rule says every number must be placed. A correct puzzle answer satisfies every condition, not just one side.
Start with the side that already has the most information. If two numbers are known, the missing number can be found by subtraction. If only one number is known, list possible pairs and test them calmly.
In a bigger puzzle, record each trial instead of erasing everything from memory. A small table with “side 1, side 2, side 3” keeps the work organised.
- A group spends Rs 318 from Rs 500.
- Change should be 500 – 318 = 182.
- Check by adding 318 + 182.
Answer: 318 + 182 = 500, so the change is correct.
For puzzles, a rough-work table helps. Write each side sum, circle the side that is too high or too low, and change one number at a time.
Practice Time
Try each original question first. Open the answer only after your own attempt.
Before opening an answer, do one of these checks: make an estimate, add back after subtraction, or explain the story in one sentence. If your answer changes after checking, write the corrected answer neatly and notice which check helped.
For money questions, draw a simple paid-cost-change bar if needed. The full bar is the amount paid, one part is the cost, and the other part is the change. This picture works even when the numbers are large.
Practice 1. Add: 347 + 268.
Answer: 615.
Practice 2. Estimate 489 + 312 by rounding to the nearest hundred.
Answer: About 800.
Practice 3. A bag costs Rs 235. Paid Rs 500. What is the change?
Answer: Rs 265.
Practice 4. Subtract: 704 – 389.
Answer: 315.
Practice 5. A class collected 276 paper cups on Monday and 198 on Tuesday. How many altogether?
Answer: 474 cups.
Practice 6. A notice board had 650 pins. 275 were used. How many remain?
Answer: 375 pins.
Practice 7. A shopkeeper returned Rs 46 after a Rs 200 payment. What was the cost?
Answer: Rs 154.
Practice 8. Which is closer to 600: 284 + 318 or 410 + 260?
Answer: 284 + 318 = 602, so it is closer to 600.
Practice 9. A puzzle side has 8 + 7 + __ = 21. Find the missing number.
Answer: 6.
Practice 10. Explain why estimating before adding is useful.
Answer: It helps us notice if the exact answer is sensible.
Quick Self-Check
Use these five checks after the worksheet.
Self-check 1. When do we regroup in addition?
Answer: When ones make 10 or more, or tens make 10 or more.
Self-check 2. How do we check change from Rs 500?
Answer: Add cost plus change and see whether it equals Rs 500.
Self-check 3. Why should numbers be aligned in columns?
Answer: Ones, tens, and hundreds must be added or subtracted with the same place value.
Self-check 4. What is one safe estimate for 704 – 389?
Answer: About 700 – 400 = 300.
Self-check 5. What should a word-problem answer include?
Answer: A number and the object or unit, such as learners, pins, or rupees.
Kaizen step: Estimate once, calculate once, and check once. That quiet three-step habit makes big numbers feel friendly.
Continue Learning
- Explore Class 4 Mathematics guides
- Browse PrincipalSaab Study Notes
- Open the CBSE learning hub
- Next in Maths Mela: Weigh it, Pour it