I wonder how many floors are in my apartment altogether. Since there are 61 floors above ground level and 1 floor below ground level you would need to find the difference, 61 - (-1)= 62. The difference between the highest and lowest floor in my apartment is 62.
Today I walked -2 x 5= -10 floors from the 20th floor. My final location would be 40 floors above my apartment. Since I live on the 30th floor, 10 floors below the 20th floor would equal 40 floors above me. Therefore, my location is +40.
Yesterday, I walked down 90 feet in 9 minutes. -90/9= -10 feet per minute. Today, I walked down 240 feet in 12 minutes. -240/12= -20 feet per minute. Therefore, I walked faster today.