Solving Rate Problems

[chris.hartline]

In rate problems such as #14 and #15 of the strategy guide it is not clear how to set up the final equation to solve. What is the method for solving these problems? I have looked in the strategy guide and it isn't exactly clear.

thanks

[Ben Ku]

Hi Chris,

Please remember that when you post a question about the Strategy Guides, to list which strategy guide you're looking at, which edition of the strategy guide, and the page/chapter that your question pertains to.

I am assuming you are using the 4th edition of the Strategy Guides.

One tip I have for rate problems is to draw a picture to visualize what's going on. In question #14 (Kyoto to Tokyo train problem), I drew two dots to represent the two cities, and arrows to indicate the direction of the trains heading toward each other. Once I can visualize what's going on, it's a bit easier to set up the equation.

In #14, we can see that at the point they meet, the two trains have traveled the length of the distance between the two cities:
D(train K to T) + D(train T to K) = 300
so when we throw in the info from the chart:
240(t + 1/6) + 160t = 300.

In #15 (Nicky and Cristina), if we draw a picture, we can see the distance that Nicky runs is the same as the distance Cristina runs, since they start at the same spot, and they will meet when Cristina catches up. So from the chart,
D(Cristina) = D(Nicky)
5t = 3(t+12)

Hope that is more clear.