Good Learning Co.
SavannahYear 8
← Maths
MathsNumber sense22 min★ difficulty

Rounding and estimating to check answers

A quick rounded estimate is your safety net — if your calculator answer is wildly different, you know something went wrong before you hand in the work.

Part of your national curriculum
  • Number: Round numbers and measures to an appropriate degree of accuracy and use approximation to check answers

Lesson overview

What you'll learn in this lesson

Round numbers and measures to an appropriate degree of accuracy and use approximation to check answers

Key learning points

  • • Rounding rules
  • • Worked example
  • • Using estimates to check

This lesson at a glance

  • 22 minutes
  • 13 parts to scroll through
  • 3 quick checks
  • Marked quiz at the end
  • Gentle pace: short sittings with pauses

Words to know

numbersmeasuresappropriatedegreeaccuracy

Scroll down — the lesson carries on below

Part 1 of 13 · Discover8%
1

Watch & discover

Part 1 of 13

Watch first

Rounding and estimating to check answers

An English teaching video on this topic from MathTalk. Watch it, then scroll down for the lesson.

In a nutshell

Round numbers and measures to an appropriate degree of accuracy and use approximation to check answers

2

Learning cycle

Part 2 of 13

Learning cycle 1 of 2

Part 1 · Rounding rules

A short piece of teaching, then a check to make sure it has landed.

3

Explore the idea

Part 3 of 13

Learn

Rounding rules

To round to a given place value, look at the next digit: 5 or more rounds up, below 5 rounds down. 47.3 rounds to 47 (nearest whole), and 462 rounds to 500 (nearest hundred).

4

Explore the idea

Part 4 of 13

Learn

Worked example

Estimate 38 × 21 by rounding to the nearest 10: 40 × 20 = 800. The actual answer, 798, is very close, confirming the calculation is sensible.

5

Quick check

Part 5 of 13

Quick check

Round 462 to the nearest hundred.

6

Reset break

Part 6 of 13

Pause

That's sitting 1 of 2 done

Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.

Stop here for now
7

Quick check

Part 7 of 13

Quick check

Estimate 38 × 21 by rounding to the nearest 10.

8

Learning cycle

Part 8 of 13

Learning cycle 2 of 2

Part 2 · Using estimates to check

A short piece of teaching, then a check to make sure it has landed.

9

Explore the idea

Part 9 of 13

Learn

Using estimates to check

If a bill calculation gives £1,245 for 3 items at about £40 each, the estimate 3 × 40 = £120 shows something has gone very wrong — you would recheck the working.

10

Quick check

Part 10 of 13

Quick check

Why use estimation before an exact calculation?

11

Challenge round

Part 11 of 13

Game · Sort it

Which of these are true?

Drag each card into the right column. Tap a card first if dragging is fiddly.

True

Not true

12

Mastery quiz

Part 12 of 13

Marked quiz

End of lesson quiz: Rounding and estimating to check answers

3 questions, marked with the reasoning shown. No timer.

  1. 1. Round 462 to the nearest hundred.

  2. 2. Estimate 38 × 21 by rounding to the nearest 10.

  3. 3. Why use estimation before an exact calculation?

13

Lesson round-up

Part 13 of 13

Lesson round-up

Ready when you are

Quiz score

Not sat

Games

Not played

Points this lesson

0

Best run

0 in a row

Luna: 0 out of 3 on the practice checks. Only if you feel up to it — one more?

Ask Luna

Do the work

Your written work for this lesson

This is the part you'd do in your book at school. Pick the pieces below, write here or on paper, and photograph anything you draw or work out.

Article

The cost of a school trip

A school is planning a trip to a wildlife park. The coach costs £480 however many people go. Entry costs £9.50 for each pupil and each adult goes free. The school says every pupil must pay the same amount, and the trip must not lose money.

If 60 pupils go, the coach works out at £8 each, so the total for each pupil is £17.50. If only 40 pupils go, the coach works out at £12 each, so the price rises to £21.50. The teacher explains that the coach is a fixed cost and the entry is a cost per person — which is why the price per pupil changes when the number changes.

The school decides to charge £20 and to use anything left over for a second trip later in the year.

Written for Good Learning Co.

Reading questions

  1. Work out the total cost of the trip if 50 pupils go.
  2. Show why the price per pupil falls when more pupils go, using numbers.
  3. At £20 each, how many pupils must go before the trip makes money? Show your working.

  • Working out

    Working out

    Do the practice questions on paper, showing every step — not just the answer. Mark them yourself and circle anything you got wrong.

    10–15 questions

  • Worked example, explained

    Writing

    Copy one question out and write underneath, in words, why each step works.

    1 question, 4–5 sentences

  • Problem in words

    Working out

    Write your own real-life problem that uses today's method, then solve it.

    1 problem + solution

Saved as you type.

Part 1 of 13 · Watch & discover

How this is going

  • Not looked at yet

    Round numbers and measures to an appropriate degree of accuracy and use approximation to check answers

Good Learning Co. — personalised UK curriculum learning, built around what each learner loves.