Trace Through Compression Decisions

Work through compression scenarios step by step

How to Use This Activity

Work through each scenario step by step. Enter your answer, then check if you're correct before moving on. This helps you understand the decision-making process for choosing compression types.

Exercise 1: Compressing a Text Document

A student needs to email their 5 MB Word document. The email limit is 10 MB. Trace through the decision process.

Step 1: What type of file is a Word document? (text/media)

Step 2: Can text documents have any data loss? (yes/no)

Step 3: Which compression type must be used? (lossy/lossless)

Step 4: If ZIP achieves 60% reduction, compressed size = 5 × 0.4 = ? MB

Exercise 2: Holiday Photo Storage

100 photos at 20 MB each need to fit on a 500 MB memory card. Trace through the options.

Step 1: Total uncompressed size = 100 × 20 = ? MB

Step 2: Space available = 500 MB. Do photos fit uncompressed? (yes/no)

Step 3: Photos can accept slight quality loss. Which compression? (lossy/lossless)

Step 4: JPEG at 90% compression: new size = 2000 × 0.1 = ? MB

Step 5: Does 200 MB fit on 500 MB card? (yes/no)

Exercise 3: Calculating Compressed File Sizes

An uncompressed music file is 80 MB. Calculate sizes for different compression levels.

Lossless (FLAC)

Step 1: FLAC achieves 35% reduction. Remaining = 100% - 35% = ?%

Step 2: FLAC size = 80 × 0.65 = ? MB

Lossy (MP3 320kbps)

Step 3: MP3 achieves 85% reduction. Remaining = 100% - 85% = ?%

Step 4: MP3 size = 80 × 0.15 = ? MB

Comparison

Step 5: How many times smaller is MP3 than FLAC? (52 ÷ 12, round to 1 decimal)

Exercise 4: Software Download Decision

A game developer needs to distribute a 4 GB game. Trace through the compression choice.

Step 1: Game files include code and executables. Can any bits be changed? (yes/no)

Step 2: If bits are changed, what happens? (works/corrupted)

Step 3: Which compression type is required? (lossy/lossless)

Step 4: Lossless achieves 40% reduction on game files. Size = 4 × 0.6 = ? GB

Step 5: Common format for software distribution? (zip/jpeg)

Exercise 5: Video Streaming Quality

A streaming service offers different quality levels. A 2-hour movie at full quality is 50 GB uncompressed.

Step 1: Video is watched once, then discarded. Is perfect quality essential? (yes/no)

Step 2: Which compression can achieve greater size reduction? (lossy/lossless)

Step 3: HD streaming at 95% compression: size = 50 × 0.05 = ? GB

Step 4: SD streaming at 98% compression: size = 50 × 0.02 = ? GB

Step 5: What's the trade-off with higher compression? (quality/speed)

Exercise 6: Hospital Database Backup

A hospital needs to backup 500 GB of patient records including scanned documents and X-rays.

Step 1: Could missing or altered data harm patients? (yes/no)

Step 2: Must the backup be bit-for-bit identical? (yes/no)

Step 3: Which compression type must be used? (lossy/lossless)

Step 4: Lossless achieves 45% reduction. Backup size = 500 × 0.55 = ? GB

Step 5: Even X-ray images use lossless. Why? (convenience/accuracy)

Exercise 7: Website Speed Optimization

A webpage has 8 images at 3 MB each. Page load time is too slow.

Step 1: Total image size = 8 × 3 = ? MB

Step 2: Are website images viewed at high zoom? (yes/no)

Step 3: Slight quality loss acceptable for web? (yes/no)

Step 4: JPEG at 85% quality achieves 90% reduction. New total = 24 × 0.1 = ? MB

Step 5: If original loaded in 12 seconds, new load time = 12 × 0.1 = ? seconds

Exercise 8: Understanding Generation Loss

A photo is edited and saved as JPEG 5 times. Each save loses 5% quality from the previous version.

Step 1: After save 1, quality = 100% - 5% = ?%

Step 2: After save 2, quality = 95% × 0.95 = ?% (round to 1 decimal)

Step 3: What is this degradation effect called? (generation loss/pixel loss)

Step 4: Does generation loss occur with PNG? (yes/no)

Step 5: To avoid generation loss when editing, use which compression? (lossy/lossless)

Your Progress

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