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Mathematics · Grades 2–5

Find the mistake: number sense

A correction is stronger when it names the mistaken rule or place value.

Make a worksheet

Understand the idea

Explain the step

A correction is stronger when it names the mistaken rule or place value.

Estimate first

An estimate can reveal an unreasonable result before detailed checking.

Examples and reasoning

A pupil says 48 + 27 = 615 because 4 + 2 = 6 and 8 + 7 = 15. Correct the answer and explain.

48 + 27 = 75. Regroup 15 ones as 1 ten and 5 ones; 4 + 2 + 1 = 7 tens.

48 + 27 = 75. Regroup 15 ones as 1 ten and 5 ones; 4 + 2 + 1 = 7 tens.

A pupil says 302 − 198 = 196. Use a nearby-number strategy to correct it.

302 − 200 + 2 = 104. Subtracting 200 removes two too many, so add two back.

302 − 200 + 2 = 104. Subtracting 200 removes two too many, so add two back.

Check your understanding

  1. Which is a useful estimate for 49 × 6?

    1. 49 + 6 = 55
    2. 500 × 6 = 3000
    3. 50 × 6 = 300
    4. 5 × 6 = 30

  2. In 508, what does the digit 5 represent?

    1. 50
    2. 0.5
    3. 500
    4. 5

  3. A pupil says 6 × 4 must equal 6 + 4. Explain the difference.

  4. Use the inverse operation to solve □ ÷ 7 = 8.

Answers and marking notes

Answers and marking notes
  1. 50 × 6 = 300

    50 × 6 = 300

  2. 500

    500

  3. Multiplication can represent six equal groups of four, totaling 24; adding 6 and 4 gives 10.

    Multiplication can represent six equal groups of four, totaling 24; adding 6 and 4 gives 10.

  4. 56

    8 × 7 = 56

Learning preview · teacher review required. Grade bands are approximate, not official curriculum alignment.