Google Sheets – Calculate Remaining Duration Based on Percentage

Ultimately, all I'm trying to do is calculate completed hours based on percentages from an original duration. I have the following in Google Sheets (manually entered for display):

The only columns I would like to manually enter values in, is the "Course Hours" and "Complete %". The "Completed Hours" and "Remaining Hours" columns are then calculated based on those values.

I couldn't find any built-in functions on Google Sheets to do this and nothing out there seems to address the simple duration – % = remaining time scenario, unfortunately. I've also used some custom functions passing in values from the columns, however the JavaScript ends up outputting values where the final duration values are off (the usual floating point calc issues with JavaScript).

I'm sure there is a simple answer I'm overlooking here.