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Computer science · Grades 6–10

Compare compressed sizes

Use the same size units; file-size reduction alone does not prove quality is preserved.

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The key idea

Use the same size units; file-size reduction alone does not prove quality is preserved.

saved % = (original − compressed)/original × 100

Worked examples

A file shrinks from 1480 KB to 444 KB. What percentage of its original size was saved?

(1480 − 444)/1480 × 100 = 70%

70 %

A file shrinks from 620 KB to 155 KB. What percentage of its original size was saved?

(620 − 155)/620 × 100 = 75%

75 %

Try it yourself

  1. A file shrinks from 1700 KB to 255 KB. What percentage of its original size was saved?

  2. A file shrinks from 680 KB to 306 KB. What percentage of its original size was saved?

Check your understanding

Answers and marking notes
  1. 85 %

    (1700 − 255)/1700 × 100 = 85%

  2. 55 %

    (680 − 306)/680 × 100 = 55%

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