[FMX] Convert Decimal Time To Standard Format

hi all,
I am in a bit of a fix.
I am trying to do a calculation which will eventually (hopefully) yield the total length of time it will take to download a certain size file over different broadband speeds.

//amount_total is the total file size (GB)
//multiplied by 1024 to give me total megabytes
mb = Number (amount_total*1024)
//15 is time (s) to download 1MB
//Dividing by 3600 gives me a DECIMAL TIME
time_512 = Number ((mb * 15)/3600)

So, I am left with a total time of eg: 4.5 hours.
Now, ideally, i would like a standard number I can use across my movie to convert 4.5 hours to 4hrs 30, or 4.30 for simplicity.
If I have 0.5 hours as a total, it would be much easier for the user to read it .30 hours.

Is this too confusing ?