Number 5

3 marks · Normal

Estimate the value of 43.7 × 8.2 by rounding each number to 1 significant figure before multiplying.

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400 (±20)

Also accept: 400; ~400

Common mistakes: Not rounding to 1 s.f.; Not using estimation - calculates exact answer

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Marking points

M1 · 1 mark · Rounds 43.7 to 40 (or 40, 44, 1 s.f.) and 8.2 to 8 (to 1 s.f.).

M2 · 1 mark · Multiplies the rounded numbers correctly.

A1 · 1 mark · Gives answer as 320 or 400 (accept minor rounding error) and identifies as an estimate.

Worked solution

43.7 ≈ 40 (1 s.f.), 8.2 ≈ 8 (1 s.f.)

Also accept 44 × 8 = 352 or 40 × 10 = 400. Typical answer: 320 or 400 (estimate).