AP CSP Day 46: Software Licenses
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Practice Question
A video file is compressed using lossy compression, reducing its size from 500 MB to 50 MB. Which of the following statements are true?
I. Some visual or audio quality has been permanently lost.
II. The original 500 MB file can be perfectly reconstructed from the compressed version.
III. The compression achieved a 10:1 ratio.
Statement I is true: lossy compression permanently removes data, resulting in reduced quality. Statement III is true: 500 MB / 50 MB = 10:1 compression ratio. Statement II is false: lossy compression permanently discards data, so the original cannot be perfectly reconstructed.
B) Statement III is also true (simple division confirms the ratio). C) Statement II is false because lossy compression is irreversible. D) Statement II is false, so not all three are correct.
Students sometimes think lossy-compressed files can still be restored to their original quality. The word "lossy" specifically means some information is permanently lost in the compression process.
Compression ratio = original size / compressed size. Lossy = permanently removes data (irreversible). Lossless = preserves all data (fully reversible).
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