I had a go at this question as I was writing my comment that had the 9 marbles puzzle in it. So here is what I was thinking during that time:
Of course, obviously 100 minutes but I don't trust my mind. Then I noticed the simplification of 5-5-5 to 1-1-1 did not make sense since 1 machine, 1min makes 1 wedge means 5 machines, 1min makes 5 wedges. So the correct simplification of 5-5-5 is 1-5-1 as each machine starts and ends at the same time and no machine is off while others are working.
So ans is 5min.
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By the way, can you explain the purpose of your comment earlier?
This one:
"Looking at research and research degrees in mathematics, it is clear that 90% is based on existing results. Most PhD students generalise and specialize existing research, yes? (unless you are John Von Neumann)."