Answer :
Let's look at the math; half a disk takes 40 seconds to rip, and two halves make a whole, so 40 + 40 = 80 and that's your answer
Well, A whole would be 100, but if you did it in half it would be 50/50! But since, you dont have 50 on one side, then you would do 60/40 and you would get 20, I think this is how you would do it. I hope I helped and didn't confuse you. :)