Answer:
To calculate the number of hours of bike use per dollar, we can divide the number of hours by the cost in dollars.
Given that it costs $21 to rent a bike for 4 hours, we can calculate the number of hours per dollar as follows:
Number of hours per dollar = (Number of hours) / (Cost in dollars)
Number of hours per dollar = 4 hours / $21
Simplifying this expression, we get:
Number of hours per dollar ≈ 0.1905 hours per dollar
Therefore, a customer gets approximately 0.1905 hours (or 11.43 minutes) of bike use per dollar at Cheng's Bike Rentals.