Getting Time Remaining - math

Question

Say something happens at a rate of 5000 per hour and there's some amount remaining (let's say 2500 for example's sake).
How would I get the hours, minutes, and seconds remaining?
I would think it'd be something along the lines of:
hour = floor(remaining / perHour)
mins = floor(remaining % perHour / 60)
secs = floor(remaining % perHour % 60)
However calculating that back up using the below returns the incorrect amount.
time = hour + (mins / 60) + (secs / 60 / 60)
time * perHour // 3472.2 - not 2500
The time should be shorter so I'm obviously calculating this wrong. I would appreciate it if someone were to explain where I went wrong.
EDIT: I'm aware this isn't the Maths SE but the Maths SE is supposed to be for high level maths, and this is the next best fit.
Figured out a method, but it may not be the best so I'll leave this question up for a while longer.
hour = floor(remaining / perHour)
mins = floor(remaining / perHour * 60) - hour * 60
secs = floor(remaining / perHour * 3600) - mins * 60 - hour * 3600

Answer 1

Our question is how much time remains, and we know the rate of the process. No sweat, we establish a rate ( Items/minute, Items/sec) and divide the number of remaining elements by the rate. We could use any unit of time we want as long as we keep it consistent -- personally, I like rates in per-second because Hz.
A Demo
function getRemainingTime(remainingItems) {
const processRatePerHour = 5000;
const processRate = (processRatePerHour / 60 / 60); // 1.3888 per second
remainingSeconds = remainingItems / processRate;
return {
hours: (remainingSeconds / 3600),
minutes: (remainingSeconds / 60),
seconds: remainingSeconds
};
}
function showProgress(remainingItems) {
var time = getRemainingTime(remainingItems);
var list = document.createElement('ul');
var processEnd = moment().add(time.seconds, 's');
list.innerHTML = `
<ul>
<h3> With ${remainingItems} remaining, we will be finished ${processEnd.fromNow()}. </h3>
<li> Hours Remaining: ${time.hours} </li>
<li> Minutes Remaining: ${time.minutes} </li>
<li> Seconds Remaining: ${time.seconds} </li>
</ul>`;
document.body.appendChild(list);
}
// Let's try it out!
showProgress(4999);
showProgress(2500);
showProgress(100);
body {
font-family: 'Helvetica', sans-serif;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.19.2/moment.min.js"></script>
<h2> Please Accept My Answer v.0.2. </h2>