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

Question

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.

In: 8653

Answer 1

I’ll try to explain visually.

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100% Speed (15 min): |#####|#####|#####|

150% Speed (10 min): |#####|#####|

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As you can see, the 10 min video is roughly the same size as 2/3 of the 15 min video, so it’s 1/3 (33%) faster.