Originally Posted by
Brett Luna
t = d/v
Just because you don't show your work doesn't mean it isn't algebra.
Yes! Another example of algebra simplifying a problem! Done by a fifth grader...
The problem was the classic fly on the trains.
There is a train on a track in Muscatine, IA, going west at 2mph. There is another train on the same track in Des Moines, IA, going east at 3 mph. There is a fly on the front of the train in Muscatine, it flies at 7 mph straight to the Des Moines train then immediately turns around, flies back to the Muscatine train, then back to the Des Moines train, and so on.. till the trains collide!
The fly begins its journey when the trains are at speed and 150 miles apart.
How far does the fly fly?
Most of my class struggled with this. Then one student answered correctly.
Me: "Outstanding! how did you get this answer?"
Lori: "Well, you said we don't do hard problems, so I changed it to a simple problem.
If I was driving 10 mph and I wanted to know how far I have gone I need to know how long I was driving, then multiply. So if I wanted to know how far the fly went I need to know how long it was flying. So the real problem is how long before they crashed. Then you just multiply"
She came up with a general formula, inputted the data specific to this problem, then it was just arithmetic. The essence of teaching math.
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