Primary 4 Four Operations of Whole Numbers Study Guide
Primary 4 whole numbers in five short steps: column multiplication, dividing and the remainder, quantities drawn as units, before-and-after changes, and supposing or grouping. Each step has a short activity, then worked examples follow.
Start here
What are the four operations of whole numbers?
Add, subtract, multiply and divide, and let the story choose.
In Primary 4 the numbers grow to four digits, so your child multiplies and divides in columns. In a word problem, the harder part is choosing which operation comes first. Drawing the amounts as bars of equal units shows the order.
In this chapter, your child learns to:
- multiply up to 4 digits by 1 digit, and up to 3 digits by 2 digits;
- divide up to 4 digits by 1 digit, and decide what the remainder means;
- draw two or three quantities as units, then find one unit;
- spot what stays the same when amounts change;
- suppose every item is one kind, or count one group at a time.
Step 1
Multiplying whole numbers in columns
Start with the ones. Multiply one column at a time, moving left. When a column makes 10 or more, write its ones digit and rename the rest into the next column. For a 2-digit number, multiply by the ones, then by the tens, and add the two partial products.
Tap Next step
What is 406 × 7?
Step 2
Division with remainders and two-step problems
Ask what the remainder means. Divide from the left, one place at a time. The remainder is what is left after the full groups. If the question asks for full boxes, leave the remainder out. If every item must be packed, the remainder needs one more box. In a two-step problem, the second step uses the answer from the first, with both amounts in the same units.
Mrs Goh cuts a ribbon 5 m long into pieces 8 cm long. How many pieces can she cut?
Step 3
Comparing quantities with units
Find one unit first. Draw each quantity as a bar of equal units. Count the units that make the total, then find one unit. When one bar is longer by a given amount, set that extra part aside before dividing. With three quantities, make whole units first, then find one unit.
Siti and her brother have 1460 stamps altogether. Siti has 3 times as many stamps as her brother. How many stamps does Siti have?
A school has 2356 pupils. There are 418 more girls than boys. How many girls are there?
Hana, Ivy and Jun share 960 cards. Ivy has twice as many cards as Hana. Jun has 3 times as many cards as Hana. How many cards does Jun have?
Step 4
Before and after: what stays the same
Look for the part that does not change. When one person gives some to another, their total stays the same. When both gain or lose the same amount, the difference stays the same. When only one amount changes, the other stays the same. Draw the after bars around the part that stayed.
Box A and Box B have 270 cards altogether. 35 cards move from Box A to Box B. Then Box B has twice as many cards as Box A. How many cards were in Box B at first?
Ravi has $170 and Mei has $80. Each of them spends the same amount on a book. Then Ravi has 4 times as much money as Mei. How much does the book cost?
Ali has 3 times as many stickers as Ben. Ali buys 120 more stickers. Now Ali has 5 times as many stickers as Ben. How many stickers does Ben have?
Peter gives 15 of his marbles to his sister. What stays the same?
Step 5
Supposition and grouping problems
Suppose, then swap. When there are two kinds of item, suppose they are all one kind. Find how far that is from the real total, then divide by what one swap changes. In a grouping problem, build one group, find what it holds, then count the groups.
A car park has 20 vehicles. Some are cars with 4 wheels and the rest are motorbikes with 2 wheels. There are 56 wheels in all. How many motorbikes are there?
Tap Swap
A shop gives 1 free pencil for every 4 pencils bought. Mei Ling takes home 30 pencils. How many pencils did she pay for?
Primary 4 whole numbers questions, worked step by stepHave a go on paper first. Open the hint if you need it, or reveal the working one line at a time.
A bakery bakes 245 trays of buns. Each tray holds 36 buns. How many buns does the bakery bake?
- 245 × 6 = 1470.
- 245 × 30 = 7350. Write 0 in the ones first, then multiply by 3.
- Add the partial products: 1470 + 7350 = 8820.
Mrs Lim bought 4 kg of rice. She cooked 1250 g of it and packed the rest equally into 5 containers. How many grams of rice were in each container?
- 4 kg = 4000 g.
- Rice left: 4000 − 1250 = 2750 g.
- Each container: 2750 ÷ 5 = 550 g.
Amir has 132 stamps and Farid has 48 stamps. They each give away the same number of stamps. Then Amir has 4 times as many stamps as Farid. How many stamps did each boy give away?
- Difference: 132 − 48 = 84, before and after.
- After, Amir is 4 units and Farid is 1 unit, so 3 units = 84.
- 1 unit = 84 ÷ 3 = 28. Farid has 28 stamps left.
- Each gave away 48 − 28 = 20 stamps.
A library has 2355 books in English, Malay and Chinese. There are twice as many English books as Malay books. There are 145 more Chinese books than English books. How many Chinese books are there?
- Malay: 1 unit. English: 2 units. Chinese: 2 units and 145 more.
- 5 units = 2355 − 145 = 2210.
- 1 unit = 2210 ÷ 5 = 442.
- Chinese books: 2 × 442 + 145 = 1029.
A quiz has 25 questions. Each correct answer scores 4 marks, and 1 mark is deducted for each wrong answer. Joel answered every question and scored 70 marks. How many questions did he answer correctly?
- If all were correct: 25 × 4 = 100 marks.
- 100 − 70 = 30 marks fewer than that.
- Each wrong answer loses its 4 marks and 1 more: 4 + 1 = 5 marks.
- Wrong answers: 30 ÷ 5 = 6. Correct answers: 25 − 6 = 19.
Step 6
Check yourself
Five short questions, one for each step. Nothing is saved; each answer points to the practice that fits.
1. What is 2047 × 8?
2. A minibus takes 9 pupils. How many trips are needed to take 230 pupils?
3. Two numbers add up to 1500. One is 300 more than the other. What is the smaller number?
4. Dan has 50 more marbles than Eli. How many must Dan give Eli so that they have the same number?
5. 10 bicycles and tricycles have 24 wheels in all. How many tricycles are there?
How to use this guide. Do Step 1 on paper beside the screen, one column per tap, and let your child say each renamed digit aloud. In Steps 3 and 4, ask which bar is longer, and by how much, before tapping Next. A step takes a few minutes; the whole guide about twenty.
The worked examples move from a straight calculation to stories that need a drawing. Cover the working, let your child sketch the bars, then reveal one line and compare it with theirs.
More study guides
P4 Four Operations of Whole Numbers lessons and practice
10 lesson videos and 67 questions across ten subtopics, from Basic to Challenge, each with a worked solution.
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