What would be the best way to drop whole part of a decimal number in PowerShell?

I have a number 102 which represents 102 seconds.

I want to drop minutes out of these seconds such that the result if free of minutes.

There result (calculation) should therefore be something along this:

split minutes and seconds: 102 / 60 = 1.7

drop minutes: 1.7 - 1 = 0.7

calculate seconds: 60 * 0.7 = 42

If I got this right, this means there are 42 seconds (and 1 minute which is not important right now)

Test is true: 1 * 60 + 42 = 102 // OK

I need the most efficient and conventional way to calculate this preferably by using .NET, but pure PowerShell version is fine too.