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Practice sheet · Media Path · Lens 1: Math

Ratios & frames

Practice for The Math of Media: aspect ratios, frame rates, thirds, pixels, misleading numbers and feed formulas (pp.4–9), plus Algebra A1–A2 (pp.10–11).

Warm-upCoreLevel Up

Name Date Time I spent

Remember

Aspect ratio: divide width and height by their biggest common factor. Frames = seconds × fps. Slow motion = recorded fps ÷ playback fps.

Pixels = width × height; uncompressed, each pixel takes 3 bytes. Percent change = change ÷ start. Toy feed score = (L + 3C + 5S) ÷ (H + 2) (p.9).

Warm-up

One step

Ratios, frames and thirds.

Simplify

Write 2560 × 1440 and 1080 × 1350 as simplified aspect ratios.

Count frames

How many frames are in a 12-second clip at 24 fps?

Slow-mo

You record at 240 fps and play back at 30 fps. How many times slower is it? How long do 1.5 real seconds last on screen?

Thirds

Where are the rule-of-thirds lines on a 1920 × 1080 video, in pixels from the left and from the top?

Core

Two or three steps

Write the formula, then the numbers.

Pixel count

How many pixels are in a 1280 × 720 frame? About how many megapixels? How many times as many does 4K (8,294,400) have?

File size

Uncompressed, how many bytes is one 1280 × 720 frame? About how many MB is 10 seconds at 30 fps? Why do phones compress video?

Media Practice · Media Path · Unizon1/2

Media Path · Unizon · PracticeRatios, frames & percent

Chopped axis

Channel A: 14,500 views. Channel B: 15,200. How many percent more did B get? If the chart’s axis starts at 14,400, how many times taller does B’s bar look?

Percent of what?

A post went from 5 views to 20. What is the percent increase? Why can that headline mislead?

Rank the feed

Score two posts with the toy formula. Post 1: L = 90, C = 12, S = 6, H = 3. Post 2: L = 300, C = 5, S = 9, H = 10. Which shows first?

Golden ratio

Continue 1, 1, 2, 3, 5, 8, 13, 21 to 34 and 55. Find 34 ÷ 21 and 55 ÷ 34 to 3 decimal places. What number are they closing in on?

Level Up

Equations

A1–A2 (pp.10–11).

Solve for a side

A 9:16 video is 1280 pixels tall: w = 9h ÷ 16. How wide is it? A 4:5 post is 1350 tall: how wide?

Solve for time

At 24 fps, F = 24s. How long is a 600-frame clip? Shot at 240 fps, how much real time do 600 frames cover?

Catch up

How many likes would Post 2 need to beat Post 1’s score? Solve (L + 60) ÷ 12 = 31.2, then round sensibly.

Pixels are quadratic

A 16:9 screen has 921,600 pixels. Solve (16 ÷ 9)h² = 921,600 for its height. What are its width and height?

Make your own problem

Your turn to be the content creator

Pick a video, photo or chart you’ve seen this week.
Write a question about its ratio, frames, pixels or a percentage.
Solve it, then ask: is the number shown honestly?

My problem, and my worked answer:

Media Practice · Media Path · Unizon2/2

Media Path · Unizon · PracticeRatios, frames & percent

Try every problem first, then check here. Wrong answers are useful: find the step where your work and the key split apart.

The key never prints with Print my work or Print blank. Open it to get its own Print the answer key button.

Answer key

Worked solutions. Views, likes and the feed formula are example numbers (p.9).

Warm-up

16:9 · 4:5 2560 ÷ 160 = 16 and 1440 ÷ 160 = 9. 1080 ÷ 270 = 4 and 1350 ÷ 270 = 5.

288 frames 12 × 24 = 288 separate pictures.

8× slower · 12 s 240 ÷ 30 = 8. 1.5 × 8 = 12 seconds on screen.

across 640 and 1,280 · down 360 and 720 1920 ÷ 3 = 640; 1080 ÷ 3 = 360.

Core

921,600 · ≈ 0.9 MP · 9× 1280 × 720 = 921,600. 4K is 3 times as wide and 3 times as tall: 3 × 3 = 9.

2,764,800 bytes ≈ 2.8 MB · ≈ 829 MB 921,600 × 3 = 2,764,800. 10 s × 30 fps = 300 frames: 300 × 2,764,800 ≈ 829 million bytes. Compression keeps mostly what changes.

≈ 4.8% more · looks 8× taller 15,200 − 14,500 = 700; 700 ÷ 14,500 ≈ 0.048. Above 14,400 the bars are 800 and 100 tall. Start the axis at 0.

300% (20 − 5) ÷ 5 = 3 = 300%. It is still only 20 views: always ask “percent of what?”

Post 1: 31.2 · Post 2: 30 → Post 1 first (90 + 36 + 30) ÷ 5 = 31.2. (300 + 15 + 45) ÷ 12 = 30. The age penalty beats Post 2’s extra likes.

≈ 1.619 · ≈ 1.618 They close in on φ ≈ 1.618, the golden ratio. It’s a useful tool, not a magic law (p.6).

Level Up

720 px · 1,080 px 9 × 1280 ÷ 16 = 720. w = 4h ÷ 5 = 4 × 1350 ÷ 5 = 1,080.

25 s · 2.5 real seconds 600 ÷ 24 = 25. 600 ÷ 240 = 2.5: that’s 2.5 s of action stretched to 25 s.

315 likes L + 60 = 31.2 × 12 = 374.4 → L = 314.4. 314 isn’t enough, so 315 to pass.

h = 720 · 1280 × 720 h² = 921,600 × 9 ÷ 16 = 518,400 → h = 720. Width = 16 × 720 ÷ 9 = 1,280.

Make your own: write the formula first, keep pixels, frames and seconds labelled, and check every percent: percent of what?

Media Practice · Media Path · UnizonAnswer key