It's because of how it is worded. He does not cut production TIME by 50, he increases production RATE by 50, meaning that in 8 hours, instead of producing 6 drillers, you produce 9(50% of 6 is 3, 3+6=9). That means you make 1 driller every 0.88 hours, as opposed to the regular 1.33 hours. However, for whatever reason you'd like, your factories put out the drillers they've made in sets of 6. So to make 6 drillers it would take 6*0.88 hours, which is 5.3 hours. If the concept of percentages is confusing, imagine this situation. At 100km/h you travel 100km in 1 hour. If you increase your speed by 50%, how much time would it take to travel 100km? It isn't half an hour, because that would mean you were traveling at 200km/h. You would now be traveling at 150km/h, so to travel 100km would take 2/3 of an hour(100/150=2/3). The reason a second tycoon puts your production to 4 hours is because it would be 2 50% increase. Doubling the rate of production halves the time you can produce 6 drillers in. Make sense?
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