KS2 Maths — Money, Measures & the Four Operations

Taught through what it really costs to keep an animal

Approx. 45 minutes · KS2 · Also usable as two shorter sessions

Before you start

People often ask us how much an animal costs. They usually mean the price on the label. That is almost never the real answer.

Working out the real answer is a maths job, and you can do it.

Nothing here is timed. You can look at any answer whenever you want.

Part 1 — Money: pounds and pence

Money is written with two digits after the point. Always two.

£3.5 is not a proper way to write it. It should be £3.50.

Adding money

A week's shopping for the hedgehogs:

Line up the decimal points, then add:

  £8.45
  £3.20
  £5.99
+ £2.50
-------
 £20.14

Total: £20.14

Subtracting money

You pay with £25.00.

£25.00 − £20.14 = £4.86 change

The tip that saves marks
Line the decimal points up underneath each other before you add or subtract. If they are not lined up, the answer will be wrong even when every digit is right.

Check yourself

Food costs £6.75 and bedding costs £4.40. You pay with £20. How much change?

Part 2 — Multiplying to find a longer cost

If something costs the same every week, multiply.

Food costs £8.45 a week.

• 4 weeks: £8.45 × 4 = £33.80
• 52 weeks (a whole year): £8.45 × 52 = £439.40

That is one animal's food for one year. Most people are surprised.

Check yourself

Bedding costs £5.99 a week. How much for 12 weeks?

Part 3 — Dividing to share it out

If you know a total, divide to find one part.

A big sack of food costs £36 and lasts 8 weeks.

£36 ÷ 8 = £4.50 per week

That is cheaper than buying small bags at £8.45 a week. Buying bigger costs more at once but less over time.

Check yourself

A box of mealworms costs £27 and lasts 6 weeks. What is the cost per week?

Part 4 — Measures: grams and millilitres

1 kilogram = 1000 grams
1 litre = 1000 millilitres

To go from the big unit to the small one, multiply by 1000.
To go from the small unit to the big one, divide by 1000.

A real problem

A hedgehog eats 45 g of food a day. A bag holds 2 kg.

Step 1 — get both into the same unit. 2 kg = 2000 g.
Step 2 — divide. 2000 ÷ 45 = 44.4…

So the bag lasts 44 days, with a little left over.

The step people forget
Change both numbers into the same unit before you divide. You cannot divide grams by kilograms and get anything sensible.

Check yourself

A guinea pig drinks 120 ml of water a day. A bottle holds 1 litre. How many full days does one bottle last?

Part 5 — Problems with more than one step

These look harder. They are not — they are just several easy steps in a row. Do one at a time and write each answer down.

Worked example

A hedgehog's costs for one year:

• Food: £8.45 a week
• Bedding: £5.99 a week
• Vet check: £45 once a year

Step 1 — weekly total: £8.45 + £5.99 = £14.44
Step 2 — for a year: £14.44 × 52 = £750.88
Step 3 — add the vet: £750.88 + £45 = £795.88

Nearly eight hundred pounds a year. The hedgehog itself cost £250.

What the maths shows you
The price of the animal is the small number. The care is the big number. This is true for almost every pet, and it is the reason we ask people to work it out before they buy.

Check yourself

A rabbit costs £6.20 a week for food and £3.80 a week for hay. Work out the cost for one year.

Part 6 — Questions

1. Add: £4.65 + £7.30 + £2.15 (1 mark)

2. A bag of food costs £7.25. How much do 6 bags cost? (1 mark)

3. Change these: (a) 3 kg into grams (b) 1750 ml into litres (2 marks)

4. A sack of bedding costs £24 and lasts 8 weeks. A small bag costs £4 and lasts 1 week. Which is better value, and by how much per week? (3 marks)

5. An animal eats 60 g of food a day. How many days does a 1.5 kg bag last? (3 marks)

6. Food costs £9.50 a week and bedding costs £4.50 a week. There is also a vet visit costing £60 once a year. Work out the total cost for one year. (3 marks)

If you want to go further

• Pick any animal from our care guides and work out its real cost for a year.
• Then compare that to the price of buying the animal. Which number is bigger?
• Related lessons: Fractions & Decimals · Time & Timetables · KS3 Maths — Data Handling.

Notes for the adult

Curriculum: KS2 Maths — the four operations with money and decimals; converting between metric units of mass and capacity; and solving multi-step problems in a real context.

Why the costs are real. The figures are the shape of genuine keeping costs, and the point the lesson makes in Part 5 is one Pets on the Green makes to families in person. The maths and the welfare message are the same thing here, which is unusual and worth using.

The step children lose marks on is unit conversion before dividing. Part 4 flags it explicitly and question 5 tests it directly.

For a child who finds multi-step problems overwhelming, cover everything below the current step with a piece of paper. Reducing what is visible to one line at a time works better than any amount of explanation.

Access: read-aloud, dyslexia-friendly font, enlarged text, high contrast and calm mode. Calculations are set out one step per line, and the column addition is shown in a fixed-width block so the decimal points line up on screen and in print.

No timing, no scoring. Answers are available immediately.

Ready for more? Open the full unit →