The southwest indian ridge, shown in red, moves at an average rate of 20 mm/year, making it among the ultraslow spreading ridges" on earth. in how many years will the ridge move 100 mm?

v = average speed of movement of the Southwest Indian Ridge = 20 mm/year

d = distance moved by the Southwest Indian Ridge = 100 mm

t = number of years required to move distance "d"

distance traveled is given as

d = v t

inserting the above values in the formula

100 mm = (20 mm/year) t

dividing both side by 20 mm/year

t = 100 mm/(20 mm/year)

t = 5 years