coi thời gian ban đầu là: 100%
thì thời gian lúc sau là:100%-20%=80%
vận tốc lúc sau là: 100%:80%=125%
tăng thêm là: 125%-100%=25%
dap so: 25%
25 %
dung 100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000%