Today I subbed in high school math. For "bell work" students were asked to find the perimeter of a figure. Then there's a hint (a different figure).
The teacher's slides said you could find perimeter by closing off the "cul de sacs." The perimeter is "invariant." However I really can't see how the 2nd figure has the same perimeter as the 1st figure. The 3rd slide says, "The answer is 54. " Cutting out the cul de sacs or convolutions is going to understate the perimeter. It would be like circling the Aegean peninsula and saying the circumference of that circle is the same as the linear shoreline of Greece. I am actually not quite sure the true perimeter can be derived from the first figure (assuming drawing not to scale). Am I insane? I don't know the source material of this problem.
Also IMO for sophomore geometry (high school) it's silly to say the angles are either 90 degrees or 270 degrees but maybe there's a reason.
Here are the figures:
The teacher's slides said you could find perimeter by closing off the "cul de sacs." The perimeter is "invariant." However I really can't see how the 2nd figure has the same perimeter as the 1st figure. The 3rd slide says, "The answer is 54. " Cutting out the cul de sacs or convolutions is going to understate the perimeter. It would be like circling the Aegean peninsula and saying the circumference of that circle is the same as the linear shoreline of Greece. I am actually not quite sure the true perimeter can be derived from the first figure (assuming drawing not to scale). Am I insane? I don't know the source material of this problem.
Also IMO for sophomore geometry (high school) it's silly to say the angles are either 90 degrees or 270 degrees but maybe there's a reason.
Here are the figures:
via International Skeptics Forum http://ift.tt/2elr2Rx
Aucun commentaire:
Enregistrer un commentaire