## Hinge Questions: Dilations

20 Dec

Students noticed and noted.

I wanted to be sure that they could answer a dilations question based on their observations. I had two questions premade in my set of Quick Polls. Which question would you ask?

In the past, I would have asked both questions without thinking.

I am learning, though, to think more about which questions I ask. If we only have time to ask a few questions, which questions are worth asking?

From slide 34 in Dylan Wiliam’s presentation at the SSAT 18th National Conference (2010) “Innovation that works: research-based strategies that raise achievement”.

I decided to send the second poll. I decided that if they get that one right, they can both dilate a point about the origin and pay attention to whether they are given the image or pre-image. If I had sent the second poll, I wouldn’t know whether they could both do and undo a dilation.

Next we looked at this question.

Students worked on paper first.

Then some explored with technology.

What do you want your students to know about the relationships in the diagram?

What question would you ask to see whether they did?

I asked this question to see what my students were thinking.

And so the journey to write and ask and share and revise hinge questions continues …

Posted by on December 20, 2016 in Coordinate Geometry, Dilations, Geometry

### 3 responses to “Hinge Questions: Dilations”

1. December 20, 2016 at 4:10 pm

For scale factor 3 I get OA=2.5 as well. Should be green.

• December 20, 2016 at 4:16 pm

Yes! I just took the picture before I had marked the correct response. Sorry for the confusion, and thank you for your comment.

2. December 21, 2016 at 8:28 am

Try this one….

If two points, A and B, are dilated about the origin by a factor of 3 what is the connection between AB and A’B’ ?