Step-by-step Maths Level 4 · Solving problems with the four operations · Lesson 9.1

Step-by-step Maths Level 4: Choosing one operation

Part of the Step-by-step Maths Level 4 solving problems with the four operations chapter. Chapter overview · whole chapter on one page

9.1

Choosing one operation

Level 4
Choose addition, subtraction, multiplication or division for a one-step problem with numbers to 10000

Read the problem and look for the key words. Altogether and more mean add. Left, sold and taken away mean subtract.

Equal groups mean multiply. Sharing into equal groups means divide.

Key ideas

Altogether, total, more: add.
Left, sold, taken away: subtract.
Equal groups or sharing equally: multiply or divide.

Worked example 9.1.1

Sam has 2450 stickers in one box and 1875 stickers in another box. How many stickers are there altogether?

Method. Find the key words, choose the operation (addition), then work out the answer.

Find the key words. “altogether” means put the two amounts together.
2450 and 1875
Choose the operation. Putting amounts together is addition.
2450 + 1875
Work out the answer. Add the ones, tens, hundreds and thousands with carrying.
2450 + 1875 = 4325
Write the answer. This is the total number of stickers.
4325

Check. Check: 4325 - 1875 = 2450.

Watch out. Check the answer with the opposite operation.

Worked example 9.1.2

There were 5000 cards in a shop. 1275 cards were sold. How many cards are left?

Method. Find the key words, choose the operation (subtraction), then work out the answer.

Find the key words. “sold” and “left” mean some are taken away.
5000 and 1275
Choose the operation. Taking away is subtraction.
5000 - 1275
Work out the answer. Use exchange where a column is too small.
5000 - 1275 = 3725
Write the answer. This is how many are left.
3725

Check. Check: 3725 + 1275 = 5000.

Watch out. Check with addition: the amount left plus the amount sold makes the start.

Worked example 9.1.3

72 pencils are shared equally between 8 children. How many pencils does each child get?

Method. Find the key words, choose the operation (division), then work out the answer.

Find the key words. “shared equally” means the same number in each group.
72 into 8 groups
Choose the operation. Sharing into equal groups is division.
72 ÷ 8
Work out the answer. Ask how many 8s make 72. Use the 8 times table.
8 × 9 = 72
Write the answer. This is the number for each child.
9

Check. Check: 9 × 8 = 72.

Watch out. Use the times table fact to check the division.

Watch out

Watch out. Read the whole question. The numbers do not tell you the operation; the story does.

Exam tip

Grown-up tip. Ask: “What is the question asking for? Which key word tells us the operation?”

Exercise 9A Practice: choosing one operation

Non-calculator

PSThere are 8 bags. Each bag has 91 books in it. How many books are there altogether?

Done

PS356 cards are shared equally between 4 children. How many cards does each child get?

Done

PSOmar has 2451 apples in one box and 3050 apples in another box. How many apples are there altogether?

Done

PSLily has 3586 counters in one box and 1418 counters in another box. How many counters are there altogether?

Done

PS156 stickers are shared equally between 6 children. How many stickers does each child get?

Done

PSThere are 4 bags. Each bag has 46 stickers in it. How many stickers are there altogether?

Done

PSThere are 3 bags. Each bag has 95 pencils in it. How many pencils are there altogether?

Done

PSThere are 6 bags. Each bag has 47 apples in it. How many apples are there altogether?

Done

PSLeo has 3945 cards in one box and 3275 cards in another box. How many cards are there altogether?

Done

PS603 eggs are shared equally between 9 children. How many eggs does each child get?

Done

PSThere are 8 bags. Each bag has 84 cards in it. How many cards are there altogether?

Done

PS270 counters are shared equally between 3 children. How many counters does each child get?

Done

PS497 eggs are shared equally between 7 children. How many eggs does each child get?

Done

PSThere are 6 bags. Each bag has 41 biscuits in it. How many biscuits are there altogether?

Done

PS30 stickers are shared equally between 6 children. How many stickers does each child get?

Done

PSThere were 2445 apples in a shop. 1476 apples were sold. How many apples are left?

Done