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

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%.