After the 115.5 nms, I refused to get sucked into the .05555555555 nm bit, which I now work out is actually 337.77777 feet, or 102.955 metres, not 82.5 metres, I was being sloppy above.
Therefore the correct speed reduction point is 155.55555 nms, or 102.9555metres before the 115.5 nm point.
This does assume the aeroplane slows instantly. It does not help mixing units, therefore the whole world should go Imperial. Nothing is as elegant as a nautical mile for distance purposes. We could do it if we nuke Paris.