2022 AMC 8
Complete problem set with solutions and individual problem pages
A bus takes minutes to drive from one stop to the next, and waits minute at each stop to let passengers board. Zia takes minutes to walk from one bus stop to the next. As Zia reaches a bus stop, if the bus is at the previous stop or has already left the previous stop, then she will wait for the bus. Otherwise she will start walking toward the next stop. Suppose the bus and Zia start at the same time toward the library, with the bus stops behind. After how many minutes will Zia board the bus?
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Solution 1
Initially, suppose that the bus is at Stop (starting point) and Zia is at Stop
We construct the following table of -minute intervals:
Note that Zia will wait for the bus after minutes, and the bus will arrive minutes later.
Therefore, the answer is
Solution 2
Since Zia will wait for the bus if the bus is at the previous stop, we can create an equation to solve for when the bus is at the previous stop. The bus travels of a stop per minute, and Zia travels of a stop per minute. Now we create the equation, (the accounts for us wanting to find when the bus reaches the stop before Zia's). Solving, we find that Now Zia has to wait minutes for the bus to reach her, so our answer is
