Give the step-by-step reasoning process and then the final answer. A building has 10 floors. It takes 15 seconds to go up the stairs to the even-numbered floors and 9 seconds to go up to the odd-numbered floors. This includes getting to the first floor. How many minutes does it take to get to the 10th floor?
So for all even - numbered floors (2, 4, 6, 8, 10), it takes 5 * 15 = 75 seconds. And for all odd - numbered floors (1, 3, 5, 7, 9) it takes 5 * 9 = 45 seconds. To climb all the floors, it takes 75 + 45 = 120 seconds. So it takes 120 / 60 = 2 minutes to get to the 10th floor.
The final answer: 2.