A parking garage charges $4 for each hour or partial hour a car is parked. What is the cost to park for 3.5 hours?

Any partial hour is billed as a full hour, so the cost depends on the number of hours rounded up. For $3.5$ hours, the garage bills $4$ hours: $4\cdot4=16$ dollars, choice J. Choice F ($12) charges for only $3$ hours and ignores the partial hour. Choice G ($14) multiplies the rate by the exact $3.5$ hours, which does not follow the rule. Choice H ($18) bills $4.5$ hours. This kind of rounding-up cost is a step function: the price stays flat within each hour and jumps when a new hour begins.