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Numeracy

Sanity-checking a materials order before it goes in

Estimating and checking your answer

Get close in your head first. Then check it on paper.

15 min

How the words are written:

Matched to your check-in

Round and estimate

19 packs at $48 each is about 20 × 50 = $1,000. If your calculator says $9,120, something is wrong.

Checking the order of magnitude

Ask yourself: should the answer be tens, hundreds or thousands? Most big mistakes are 10 times out.

Knowledge check

Two quick questions to show you have it.

  1. 1. Estimate 31 × 19.

  2. 2. A 3m × 4m slab at 100mm gives 12 m³ on your calculator. What went wrong?

Worksheets for this lesson

Every version is generated from this lesson. Print, save as PDF or export to Word.

  • Student worksheet

    Standard tasks with writing space.

  • Trainer answer sheet

    Every task with model answers.

  • Differentiated worksheet

    Scaffolded with sentence starters and hints.

  • Picture supported

    Visual cues beside each task.

  • Revision worksheet

    Shorter recall set for a quick review.

  • Assessment worksheet

    Marked tasks with a score box.