21.00 you would take and fine the how much 40 percent of 35 is then subtract it so 35*40/100=14 35-14=21
If you keep subtracting it, adding $2 each time the final payment would be $78
Percent literally means per one hundred so you can say:
420(55/100)
23100/100
231
You could also think of it like setting up equal ratios...
55/100=n/420
n=23100/100
n=231
Shown from studies, it would take around 1.11 seconds to fall from a 20 feet high drop.