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.

In: 8653

29 Answers

Anonymous 0 Comments

**I know others answered this already for you, but hopefully I can reorient your original logic with my explanation:**

The easiest way to think about this in terms of youtube playback is two ironclad rules:

* the maximum playback speed on youtube is 2x
* Anything ÷ 2 = exactly half the original value

So if you watch something at 2x speed, it will always be exactly *half* (50%) the original length of the video.

* A 10 minute video at 2x speed would be finished in 5 minutes. (50%)

So working backwards, if the maximum amount of time you can reduce a 10 minute video to, at 2x speed, is 5 minutes; then logically any playback speed between 1x and 2x (aka 1.25x, 1.50x, 1.75x, etc) MUST be:

* a value that is higher than 5 minutes (the maximum) aka 2x speed (50%)
* a value that is lower than 10 minutes (the original) aka 1x speed (100%)

**The above is all just moreso to re-orient the logic behind your thinking, rather than give the actual mathematical answer.**

So for the other playback speeds of a 10 min video, you’re looking at:

* 1.00x = 100% = 10:00 minute video
* 1.25x = 80% = 8:00 minute video
* 1.50x = 66% = 6:39 minute video
* 1.75x = 57% = 5:42 minute video
* 2.00x = 50% = 5:00 minute video

The actual math is kinda irrelevant to my post, since my post is moreso talking about the **logic** behind your thinking. It doesn’t correlate to understanding the math itself. But for reference:

**(calculating for 1.75x playback speed)**

* 10 min ÷ 1.75 = 57%
* 10 min ÷ 100 = 0.1 (AKA every 1% of 10 = 0.1)
* 0.1 × 57 = 5.7
* (and since we’re talking about *time,* as a unit, there’s only 60 seconds per minute. So you have to convert the decimals of 5.7 [aka the “.7”] to seconds)
* 0.7 × 60 seconds = 42 seconds
* 5 minutes + 42 seconds = 5:42 minute video

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