Monday's "twist"

When I worked on classifying the measurement/rate problems and then trying to identify what they had in common on Monday, I honed in on the fact that all of the problems dealt with units (of measurement) which are divisible.

1. So problems had hours which can be broken down into minutes and seconds or grouped as days.
2. Miles can be expressed as yards or feet and so on.
3. Dollars can be divided into cents or the various denominations on bills.

Were these problems harder to classify? I would say no, but I have learned that they are [for students]. Where I can see them being trickier or more complex is if problem 4 were changed from:

Todd's tomato plants grow 4 inches a week. How many weeks will it take for them to grow 20 inches?

to:

Todd's tomato plant grows 4 inches a week. How many days will it take for them to grow one and a half feet?

Solving the problem now requires conversion of both time and distance. So that's where I could see the problem increasing in complexity. I think that such complexity is actually desirable, but not if it is causing confusion.

Once you know that a three-sided polygon is called a triangle, I think it is purely academic and impractical to tell students "Draw a three-sided polygon and color it yellow and write the word Caution in the middle of it." BUT if we know that a tortoise moves a yard every four seconds, I WOULD expect someone to predict how many feet it may have moved in a minute. We don't talk about 180 minutes passing, we just say 3 hours. But if a TV show is 90 minutes long, we should know that it's an hour and a half in duration.