Robinson Tuition
Year 9 · Key Stage 3 · free KS3 maths worksheet

Rounding and estimating

12 original questions, 36 marks. Type your answers below for an instant mark and a score (algebra in any equivalent form, e.g. 2sqrt(3) or 2√3), or print the worksheet, mark it with the answers sheet, and use the solutions to see every step written out by hand.

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The questions

1
  1. Write 7.3846 correct to 1 decimal place.
  2. Write 7.3846 correct to 2 decimal places.
  3. Write 7.3846 correct to 3 decimal places.
  4. Write 0.0962 correct to 2 decimal places.
4 marks
Show answer
a) 7.4 b) 7.38 c) 7.385 d) 0.10
2
  1. Write 58 362 correct to 1 significant figure.
  2. Write 58 362 correct to 3 significant figures.
  3. Write 0.004718 correct to 2 significant figures.
  4. Write 3.0951 correct to 3 significant figures.
4 marks
Show answer
a) 60000 b) 58400 c) 0.0047 d) 3.10
3

Katie says

"6.2 × 48.9 = 3031.8"

Without working out the exact answer, explain how you can tell that Katie's answer must be wrong.

1 mark
Show answer
6.2 × 48.9 is roughly 6 × 50 = 300, so the answer should be close to 300, not close to 3000. Katie's answer is about ten times too big.
4
  1. Truncate 8.479 to 1 decimal place.
  2. Truncate 8.479 to 2 decimal places.
  3. Write 8.479 correct to 1 decimal place. Explain why your answer is different from your answer to part a.
3 marks
Show answer
a) 8.4 b) 8.47 c) 8.5
5

The mass of a parcel is 340 g, correct to the nearest 10 g.

Complete the error interval for the mass, m grams, of the parcel.

....... ≤ m < .......

2 marks
Show answer
335 ≤ m < 345
6

Work out an estimate for the value of

39.6 × 5.120.48

You must show your working.

3 marks
Show answer
400
7
  1. Work out an estimate for 62.3 × 4.87
  2. You are given that 623 × 487 = 303,401

    Use this fact to write down the exact value of 62.3 × 4.87

3 marks
Show answer
a) 300 b) 303.401
8

You are given that 34 × 26 = 884

Use this fact to write down the value of

  1. 3.4 × 26
  2. 340 × 2.6
  3. 0.34 × 0.26
  4. 884 ÷ 2.6
4 marks
Show answer
a) 88.4 b) 884 c) 0.0884 d) 340
9

A number d is truncated to 1 decimal place.

The result is 12.4

Complete the error interval for d.

....... ≤ d < .......

2 marks
Show answer
12.4 ≤ d < 12.5
10

A number y is 0.08, correct to 1 significant figure.

Complete the error interval for y.

....... ≤ y < .......

2 marks
Show answer
0.075 ≤ y < 0.085
11

A rectangular floor is 4.2 m long and 3.1 m wide.

Flooring costs £24.60 per square metre.

  1. By rounding each number to 1 significant figure, work out an estimate for the cost of flooring for the whole floor.
  2. Is your answer to part (a) an underestimate or an overestimate of the actual cost?

    Give a reason for your answer.

4 marks
Show answer
a) £240 b) Underestimate, because every number was rounded down
12

Tia and Sam each ran 100 m.

Tia's time was 12.4 seconds, correct to 1 decimal place.
Sam's time was 12.4 seconds, truncated to 1 decimal place.

  1. Write down the error interval for Tia's time, t seconds.
  2. Write down the error interval for Sam's time, s seconds.
  3. Tia says, "I definitely ran faster than Sam." Is Tia right? Give a reason for your answer.
4 marks
Show answer
a) 12.35 ≤ t < 12.45 b) 12.4 ≤ s < 12.5 c) No, the intervals overlap

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Every question here is original and written by Robinson Tuition. It follows the Key Stage 3 programme of study; Year 9 sheets end with extension questions for top sets.

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