Expert Human
Ms. Lindquist
240. Student: [reads the "bike-trip" problem] Cathy took a "m" mile bike ride. She rode at a speed of "s" miles per hour. She stopped for a "b" hour break. Write an expression for how long the trip took.
T1: [Doing the "bike-trip" problem] Please write an expression for the total time the trip took. [The first question always asks the student to symbolize.]
241. S: uhm [Student said "uhm" while
thinking. Then writes "s/m+b" but should be "m/s+b"]
S1: s/m+b
242. Tutor: How do you calculate the amount of time it takes you? If you’re, if you’re, if you’re riding at, let’s make it simple. If you are riding at 20 miles per hour, OK, and you go 100 miles, how many hours did that take you?
T2: No. Let me ask you an easier question. Please compute the time actually on the bikes if the speed was 20 miles per hour, and the distance ridden was 100 miles? [ask to compute a concrete instance]
243. S: Umh 5
S2: 5
244. T: 5. And how did you get that 5? How did you use the numbers 100 and …
T3: Correct. What math did you do to get that five? [ask student to articulate in symbols the answer]
245. S: 100 miles divided by miles per hour
S3: 100/20
246. T: So you took the miles and divided it by the [garbled, but possibly "speed"]
T4: Correct. Now write your answer of 100/20 using the variables given in the problem (i.e. put in ‘m’ and ‘s’)? [ask student to generalize their concrete articulation]
247. S: Miles divided by s plus b equals time [writes m/s+b]
S4: b+m/s [was expecting "m/s" but intelligently accepts this answer to a more comprehensive goal]
248. T: Right.[
T5: Correct.
