What might all these kids be proving?

Source: Ed Southall (@edsouthall)

# MathArguments180.com

180 Days of Ideas for Discussion in Math Class. (as of 9July2014, we're in overtime!)

## Saturday, October 25, 2014

## 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 ...

Same number of cans, different arrangement.

Because it's Christmas ...

## Wednesday, October 22, 2014

## 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.

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?

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?

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?

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