Friday, October 24, 2014

Thursday, October 23, 2014

289: Food Drive Cranberry Sauce

Quick, how many cans in the pyramid?


Same number of cans, different arrangement.


Because it's Christmas ...

Tuesday, October 21, 2014

287: Fahrenheit to Celsius

We all know the conversion from °C to °F: multiply by 9/5 (or 1.8, if you can't handle those evil fractions) and then add 32.

The conversion from °F to °C is more complex: subtract 32 and then multiply by 5/9 (or 0.555555555).

That's cumbersome for mental math.

Here's a shortcut: subtract 30 and divide by 2 OR multiply by 2 and add 30.

  • How good is that shortcut?
  • Are there temperatures that it's okay for and other temperatures that the shortcut is too far off?
  • Is this just another stupid shortcut? NixTheTricks ?

Monday, October 20, 2014

286: Sphereometer

How does this thing work to find curvature?


What kinds of information do you need to make the markings on that dial?

Sunday, October 19, 2014

285: Three Angles Revisited

Two days ago, I posted Okay for a Fifth-Grader?

Five Triangles said, "We posed the question slightly differently, our diagram providing an important hint to bring it to a more manageable level for younger problem solvers."


What do you suppose the "important hint" was?