*Reports that say that something hasn't happened are always interesting to me, because as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns--the ones we don't know we don't know. And...it is the latter that tend to be the difficult ones.*

**Scenario One**

You're a fifth grade teacher in the middle of a unit on finding the volume of right rectangular prisms. You pose the following task to your class, maybe as a do now, maybe on an exit card:

Find the volume of the rectangular prism. |

Question: What are you likely to find out?

Answer: Which students know how to find the volume of a rectangular prism.

**Scenario Two**

You're a fifth grade teacher in the middle of a unit on finding the volume of right rectangular prisms. You pose this task to your class, maybe as a do now, maybe on an exit card:

Tell me everything you can about this figure. |

Question: What are you likely to find out?

Answer: A whole lot more than in Scenario One.

Wait...the answer to what? There's no question! |

Hmmm. |

There's a trend developing. |

An over-achiever hits the ceiling. |

A struggler enters on the ground floor. |

*There's nothing inside.**I know this shape is made up of squares.**The perimeter is 14 units.**It's a cube, AKA a 3D square or rectangle.**It's a full cube with a top and everything else.*

Here's a breakdown of the 29 respondents who elected to identify the shape:

- cube: 13
- rectangular prism: 11
- square: 4
- special rectangular prism: 1

After looking through the responses, Rich and I realized we had some work to do. We had managed to uncover some misunderstandings and misconceptions about 3-dimensional shapes and their attributes that we didn't know existed, among both the students (What makes a cube a cube?)

*and*ourselves (Is it correct to say a rectangular prism has sides? Are the terms sides and faces interchangeable?) These and other matters would need to be addressed. But first...Remember the struggler? |

The idea for this kind of task isn't original or new. It comes from Steve Leinwand via Dan Meyer, and I came across it browsing through Dan's archives a few months ago. I tried it out again last week in a grade 4 class studying place value:

Some known unknowns surfaced, including:

Some known unknowns surfaced, including:

- Confusion about the difference between a digit and a number.
- Confusion between the value of a digit and its place value location.
- Imprecise language when trying to describe a digit's location.

And an unknown unknown:

- How do we tell if a number is odd or even?

American psychologists Joseph Luft and Harrison Ingham first came up with the idea of unknown unknowns in 1955 as part of an analytic technique they created called the Johari Window. It's a technique used by the intelligence community, and it may have beneficial applications to our field as well. The questions we ask and the tasks we pose yield information about our students. But when those questions and tasks are of a closed and narrow nature, the information we receive is limited. It may confirm or disprove what we think we know, which is no doubt important. But what

Tell me everything you can about...

*don't*we know about our students? What don't they know about themselves? What don't*we*know about*our*selves? How can we gain entry to those hidden places, where misconceptions and misunderstandings lay buried under piles of fractured definitions, half-broken algorithms, and jumbled digits and symbols?Tell me everything you can about...