If water is leaking from a certain tank at a constant rate of 1,200 mi

How many seconds does it take for 1 milliliter of water to leak from the tank?

1 hour = 3,600 seconds

Rate conversion (see below for all the conversion ratios):
\(\frac{1,200mL}{1hr}=\frac{1,200mL}{3,600secs}=\frac{1mL}{3secs}\)

One mL of water takes 3 seconds to leak from the tank

Answer D

Conversion

This conversion problem is not hard. Others will be. One way to tackle conversion problems takes very little time to learn and saves a lot of headaches when complex conversions are involved.

One hour = 3,600 seconds?

Convert with an equation set up so that the units "cancel" each other out.
Treat the units to be canceled as if they were numbers in a long set of multiplied ratios. See reference material cited below

\(\frac{1,200mL}{1hr}*\frac{1hr}{60mins}*\frac{1min}{60secs}=\frac{1,200mL}{3,600secs}\)

Cross off the units that show up opposite one another (numerator/denominator and vice versa).

In this case, hours and minutes cancel and we are left with the units we need, namely, milliliters per second.

(To get the answer to this question, we just simplify the result of the conversion equation above: \(\frac{1,200mL}{3,600secs}=\frac{1mL}{3secs}\))

For more on how to convert and cancel units, see Setting up conversion problems, here
And
Really good examples of the method, here