KöMaL 2016 K524
Andy's washing machine keeps the door locked for an additional 5 minutes after the washing program is finished: it can only be opened after this delay. Andy knows this, so he includes this period when he calculates washing times. When the machine displays that 90% of the program time has elapsed, Andy knows that 20% of the calculated washing time is yet to follow. How long is the washing program in minutes?
Official text KöMaL. Quoted with source.
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