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
5/4 speed = 4/5 time taken, i.e. shorter by 1/5
3/2 speed = 2/3 time taken, i.e. shorter by 1/3
I’ll try to explain visually.
100% Speed (15 min): |#####|#####|#####|
150% Speed (10 min): |#####|#####|
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.
Don’t feel too bad.
I know a very large multinational corporation where to executives and pricing analysts couldn’t work out that a 10% discount followed by a 10% price rise would not restore the original price.
10% off $100 is $90 but an 10% price increase on $90 is $99. They couldn’t work out where the extra $1 went.
Lol I was good and it all made sense but the I read this guys post and some comments and started to doubt myself if I actually understood this concept. After reading half the tread I realize I’m stupid and I already understood the concept just fine. Don’t second guess yourself kids
1.25x speed which can be thought of as five quarters or 5/4.
Dropping to normal speed is 1 or 4/4. you have dropped from 5 to 4 so you have dropped ‘one fifth of 5’ or 20%.
1.50x speed which can be thought of as 3 halves or 3/2.
Dropping to normal speed (2/2), you have dropped from 3 to 2 so you have dropped ‘one third of 3’ or 33%.
1 is 2/3 of 1.5. Is 4/5’s of 1.25. Is 1/2 of 2. Is twice 0.5. Those fractions are 66%, 80%, 50%, and 200% respectively.
Take the listening speed, divided by the normal speed (1), and invert it. Then subtract that value from one, or:
Change in time = 1 – (1/speed)
So 1.25 speed is divided by 1, and the inverse is 1/1.25
I don’t like decimals in my fractions, so multiply top and bottom by 4, and you get 4/5. This value represents the amount left to watch at 1.25 speed.
Subtract that from 1, you get 1/5, or 20% faster.
I wondered the same thing while listening to audiobooks while driving, and it bothered me so much I kept having to pause my book until I gave up but I eventually was able to figure this out.
**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
Let’s say you’re watching a video at 1.25 speed. That means for every one second you watch, you cover 1.25 second’s worth of video. Double it: in two seconds, you’ve watched 2.5 second’s worth of video. Double it: in 4 seconds of your life, 5 seconds have ticked by on the progress bar. Last time, let’s double it: if we watch the video for 8 seconds at 1.25 speed, we’ll have moved 10 seconds along the progress bar. If the video was 10 seconds long, then it took us 8 seconds to watch. That’s a 20% reduction in runtime. If the video was 10 minutes long, it would’ve taken us 80% of 10 minutes, or 8 minutes, to watch it at 1.25 speed: a 20% reduction in runtime.
Now we watch the video at 1.5 speed. In 1 second, we cover 1.5 seconds on the progress bar. Double it: in 2 seconds, we’ve watched 3 second’s worth of the video. Double it: in 4 seconds, we’ve watched 6 seconds of the video according to the progress bar. Now multiply it by 10: in 40 seconds, we’ll watch 60 second’s, or 1 minute’s, worth of the video. It takes us 2/3 of one minute in real time to consume 1 minute of the video according to the progress bar. That’s a 33% reduction in runtime. A 10 minute, or 600 second, video takes us 2/3 of 10 minutes, or 400 seconds, to watch at 1.5 speed: a 33% reduction in runtime.
Others are correct about inverting fractions, but when I’m struggling to understand something I like to either go big or start small. In this case, starting small and building up to round numbers that I can portion out in my head helped me out, and hopefully it helps out someone else, too.
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