Wikipedia:Reference desk/Archives/Mathematics/2021 May 16

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May 16

playspeed vs time

HELLO! i am bad at math. i got hung up when trying to watch youtube videos at non-conventional playspeeds.

like, if i watch a given video (say, 10 minutes' length) at double play speed, i think it should take 5 minutes IRL time... but how do i calculate for other speeds? like 1.5 playspeed? in short, if i want to calculate this thing, what is the question i should be asking?

similar thought: i was playing modded minecraft a while back, on a SATA SSD. assuming data transfer reading = ~600MB/sec as the sole bottleneck, and the loading takes about 20 minutes... if i upgraded to NVME SSD, one that is 10x "faster", how much time would it take (assuming all other hardware variables are the same) to do the Thing (20 minutes) 10x faster? my thought process is as follows: if it takes x amount of time to complete a task, if it is 10x faster, the result is one tenth? something something 30MPH car goes that fast per hour, double that is 60 MPH, you will have 30 miles traveled in 30 minutes. twice as fast = half the time. but what is the question i should be asking for the SSD example? purely hypothetically. 10x faster is... task complete in 1/10 of the time? so for 20 minutes, unless my math is wrong, should be 2 minutes, yes? am i over complicating things? what is the question/formula i need to solve for to answer these questions? please and thank you, have a wonderful day :)

--96.39.203.241 (talk) 05:50, 16 May 2021 (UTC)

my additional contribution to this query is: 1.5x playspeed on a 10 minute video should be... 7 minutes, 30 seconds? because half time is 5 minutes, plus half of that is 2 and a half, total is 7.5 minutes, hopefully my switching from MS to M&fractions to decimals isn't too confusing. lord knows it confuses me and might very well be the root of my consternation. --96.39.203.241 (talk) 05:55, 16 May 2021 (UTC)

Distance covered equals speed multiplied by time, so if the distance remains the same, twice the speed means half the time and ten times the speed means one tenth of the time. In a formula, if the speed is $X$ times normal, and the normal time is $T$, then the actual time is reduced by a factor of $X$ and becomes $T/X$. For a 10-minute video, $T=10\,\mathrm {m} =600\,\mathrm {s} .$ So if $X=1.5$, the actual playtime becomes $(600/1.5)\,\mathrm {s} =400\,\mathrm {s} =6\,\mathrm {m} \,40\,\mathrm {s} .$  --Lambiam 08:25, 16 May 2021 (UTC)