Question

A particular beach is eroding at a rate of 4 centimeters per year. A realtor converts this rate to millimeters per day. Which expression, when evaluated, results in the correct units and numerical value?

Answer 1

we have 4 cm= 40 mm, furthermore since 1 year contains 365 days, then 4 cm per year means:
(40/365) mm per days

Answer 2

more precisely, since 4 cm = 40 mm then the eroding rate is:
\[\Large \frac{{40}}{1}\;{\text{mm/year}}\]
furthermore, since 1 year contains 365 days, then I can rewrite such rate as below:
\[\Large \frac{{40}}{{365}}\;{\text{mm/day}}\]