The Cleanest Village
Class 4 · Mathematics
4 ideas in Class 4 Mathematics, explained in plain words, with games and quizzes to practise.
Adding with regrouping
Part of: Adding and subtracting with regrouping
Adding in columns means adding ones with ones, tens with tens and hundreds with hundreds. When a column adds up to 10 or more, we swap 10 of that kind for 1 of the next bigger kind. For example, 8 ones and 5 ones make 13 ones, which is 1 ten and 3 ones.
Why it matters. Regrouping is the base of every bigger sum, from bills to distances. Children who skip it often write each column's answer separately and get wrong totals like 717 instead of 87.
Try it in two minutes
- Take 20 small things such as beans or buttons and some bowls. Put 8 beans in one bowl and 6 in another.
- Ask: how many beans in all? Let your child count and notice there are more than 10.
- Now pack 10 beans into one cup. Ask: how many cups and how many loose beans are left?
- Write the sum in columns and show where the new ten goes. Ask your child to say it aloud: ones first, then tens.
Try at home. Ask your child to add the number of steps taken in two days, such as 268 and 175, using columns, and to explain each regrouping.
Subtracting with regrouping
Part of: Adding and subtracting with regrouping
When there are not enough ones to take away, we break one ten into 10 ones. In the same way, one hundred can be broken into 10 tens. In 52 − 27, we change 5 tens and 2 ones into 4 tens and 12 ones, and then subtract.
Why it matters. Children often subtract the smaller digit from the larger one in each column, whichever is on top. This gives wrong answers in every bill, change and measurement problem later.
Try it in two minutes
- Use 4 bundles of 10 sticks and 3 loose sticks to show 43.
- Ask your child to take away 8 sticks. Let them discover that 3 loose sticks are not enough.
- Untie one bundle to get 10 more loose sticks. Ask: how many loose sticks now? How many bundles are left?
- Take away 8 and count what remains. Write it in columns and match each step to the sticks.
Try at home. Ask your child to find the change from a play note of 500 after buying something that costs 238, and to explain each regrouping.
Estimating and quick strategies
Part of: Estimating and solving everyday problems
An estimate is a quick answer that is close to the real one. We round numbers to tens or hundreds first. For 398 + 202, we think 400 + 200, so the answer is about 600. Quick tricks help too: to add 99, add 100 and then take away 1.
Why it matters. Estimating lets children check whether an answer makes sense. Without it, a child may accept 1200 as the answer to 398 + 202 and not notice the slip.
Try it in two minutes
- Pick two prices from a shopping bill, such as 198 and 304.
- Ask your child to round each to the nearest hundred and guess the total.
- Now work out the exact total together on paper.
- Ask: how close was the guess? Would the guess have caught a mistake?
Try at home. While shopping, ask your child to estimate the total of three items before the bill is made, then compare.
Money, change and word problems
Part of: Estimating and solving everyday problems
In shopping, adding gives the total cost and subtracting gives the balance, which is the money returned. If a toy costs ₹ 46 and you pay ₹ 50, the balance is ₹ 4. Drawing a picture of the story helps to decide whether to add or subtract.
Why it matters. Handling money is one of the first real uses of maths. Children who only look for words like 'more' or 'left' may choose the wrong operation, so they need to picture what is happening.
Try it in two minutes
- Make a pretend shop with 4 or 5 items and price tags up to ₹ 100.
- Let your child choose two items and find the total cost.
- Give a play note of ₹ 200 and ask your child to work out the balance.
- Ask them to draw the story first and then say whether they added or subtracted.
Try at home. Let your child pay at a real shop and work out the change before the shopkeeper returns it.
What your child will practise
- Adding with regrouping: River Sort (Sort It Out)
- Estimating and quick strategies: Treasure Quest (Collect the Answer)
- Money, change and word problems: Desert Build (Build It)
- Money, change and word problems: Ocean Quick Fire (Quick Fire)
- Subtracting with regrouping: Jungle Puzzle (Clue Puzzle)
- Quiz: Adding with regrouping (8 questions)
- Quiz: Estimating and quick strategies (8 questions)
- Quiz: Money, change and word problems (8 questions)
- Quiz: Subtracting with regrouping (8 questions)