Can these sticks make a triangle?
Three sticks or straws of given lengths: can their ends be joined to make a triangle? The student answers yes or no, picks which of three sets makes a triangle, or works out the longest a third stick can be.
Put the longest stick at the bottom: the other two have to reach across it and meet. If together they are longer, they meet above it. If they add up to exactly the same, they lie flat, so there is no triangle. The working draws the sticks meeting, lying flat, or falling short.
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What changes each time
- Sticks or straws from 2 cm to 20 cm
- Yes, too short, or exactly flat
- One set, a choice of three sets, or the third stick's length
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