Why does watching a video at 1.25 speed decrease the time by 20%? And 1.5 speed decreases it by 33%?

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I guess this reveals how fucking dumb I am. I can’t get the math to make sense in my head. If you watch at 1.25 speed, logically (or illogically I guess) I assume that this makes the video 1/4 shorter, but that isn’t correct.

In short, could someone reexplain how fractions and decimals work? Lol

Edit: thank you all, I understand now. You helped me reorient my thinking.

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29 Answers

Anonymous 0 Comments

1.25 is 5/4.

If the video is sped up 5/4, then the time to play it back will be 1 divided by 5/4, or 4/5 (80%). To watch the whole video in that time: 5/4 x 4/5 = 20/20 = 1. 80% is 20% less than 100%.

Likewise for 1.5x: 1.5 = 3/2, so duration is 1 / (3/2) = 2/3 (67%), which is 100% – 67% = 33% shorter.

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