I tried to follow along with this units video (https://youtu.be/hQpQ0hxVNTg) and convert 60 miles per hour to light years per second. I don't get the same answer as the video does. I feel really dumb!
I just try to multiply through? and get: $$ \frac{60ly}{60*60*5.9*10^{12}sec} = \frac{1ly}{60*5.9*10^{12}sec} = \frac{1ly}{3.54*10^{14}sec} $$ or $3.54*10^{-14}$ light years per second
please halp!
The video is wrong. I have no clue where they arrived at that number.
First - note that $\frac{1}{x} \neq x$ unless $x = \pm 1$. That is,
$$ \frac{1}{3.54 \cdot 10^{14}} \neq 3.54 \cdot 10^{-14}.$$
Instead, that is equal to $2.824 \cdot 10^{-15}$ which is the correct value you should arrive at. See this Wolfram query. I also verified this on my calculators.