120÷2 means the logs of 1 floor+120, and the logs of the second floor+19 to the 60th floor +6 1 floor, that is, 65438+. The sum of these formulas is equal. 120 ÷ 2 = 60 Calculate how many regular formulas like1+1202+19 are in120.
So (120 ÷ 2) ×121= 7260 (root)
In addition: 12 1 in the formula should be written as (120+ 1), which is better.