So if you work for 8 hours everyday and you could build one dog house in 6 hours. Day one: 1 dog house. Day two: 2 dog houses. Day 3: 4 dog houses because you worked and extra 2 hours.Day 4: 5 dog houses. Day 5: 6 dog houses. Day six: 8 dog houses same reason as day 3. Day 7: 9 dog houses. Day 8: 10 dog houses. It would take 8 days to build 10 dog houses. Or 7.5 since you worked extra hours