Topic Summaries

Rounding and standard form

GCSE > Physics > WJEC > GCSE Physics Topic Summaries > Science skills: Presenting and using data > Rounding and standard form
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Science skills: Measuring results

  • To round a value to a certain number of significant figures: identify the first non-zero digit in the value and count the number of digits after this. You will round this last digit up or down depending on if the next digit is greater than or equal to 5. Remove all digits outside the count (e.g. 0.005486 ≈ 0.0589 to 3 sig figs).
  • Calculated values should be given to a number of significant figures equal to the lowest number of significant figures from the numbers used (e.g. the answer to 583 × 3.4 should be given to 2 sig figs.
  • Values are rounded to the point where they should be the same as the true value rounded to that many significant figures.
  • Standard form is used to write out very large or very small rounded numbers.
    • Write a number between 1 and 10 and multiply it by a power of 10. This can be positive or negative depending on if the number is big or small. Each multiplication by 10 moves the decimal point one digit to the left or right.
    • E.g. 158000 = 1.58 ×10⁵ and 0.00158 = 1.58 ×10⁻³

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