I'm going to go into more detail than you probably need, to try to answer any questions you have in one go. I don't frequent this site anymore so I probably won't see this thread again.

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The time will be composed of two parts - the travel time and the wait time.

Travel time is solved with the following commonplace equation: Distance = (Time)(Velocity)

The total distance is equal to the Distance from station 1 to station 2 + Distance from station 2 to station 3 + ... + Distance from station 11 to station 12, that is

.75+.75+...+.75 = 11(.75) = 8.25 miles of travel

Then we use the equation above, 8.25miles = (Time)(20miles per hour), thus Time = 8.25miles/20 miles per hour [*note: this will give us an answer in terms of hours, not minutes, so multiply by 60!]

8.25/20 = .4125 hours = **24.75min** which is the *total time spent traveling *from station to station.

Now we need to add in the wait time. Which stations will it wait at? We don't need to count the first station, because that's where it's starting (we start the watch when the train starts moving). We also don't need to count the last station because we're only interested in how long it takes to get there (we stop the clock as soon as the train pulls into station 12). So we are going to count the wait time at the 10 stations in the middle.

10(45 sec) = 450 sec =** 7.5min **which is the *total time spent waiting* at stations before getting to station 12.

Add these together, 24.75min + 7.5min =** 32.25min**

I assume whoever wrote your test mistakenly added in the waiting time for the first or last station to yield an even 33 minutes, or perhaps they rounded up. But according to the question you typed, in the way it is worded, 32 minutes 15 seconds is the correct answer.