This problem solving activity has a geometry focus.
Eva, Tamati, Noah and Jo are looking at these shapes.
Eva says, "Hey, the first shape is the odd one out."
Tamati says, "No, Eva, the second one’s the odd thing out!"
Noah says, "No, it’s the third one!"
Jo says, "Well you are ALL wrong! The last one is clearly the odd thing out."
Who is right and why?
This problem explores basic properties of 3-dimensional figures including symmetry, and number of sides (flat surfaces), lines (edges), and corners (vertices). It’s important for students to recognise basic properties of common solid figures so they can build on and refine these as they learn more. Important fundamental language of geometry is established as they correctly name and describe each figure.
There is no correct answer to this problem. Students may suggest several ideas that are not listed in the solution. Discuss these as they arise.
The Level 1 Geometry problem, Odd One Out is a problem very similar to this.
Eva, Tamati, Noah and Jo are looking at these shapes.
Eva says, "Hey, the first shape is the odd one out."
Tamati says, "No, Eva, the second one’s the odd thing out!"
Noah says, "No, it’s the third one!"
Jo says, "Well you are ALL wrong! The last one is clearly the odd thing out."
Who is right and why?
Ask the students to find other 3-dimensional objects in the classroom. Get them to say what makes them different from each other and from the four objects of the original problem.
There are multiple solutions to this problem. Eva is right because the sphere will roll no matter how you put it on the ground. Tamati is right because the cylinder is the only one that has a flat face and a curved face. Noah is right because the box is the only object that has six faces. Jo is right because only the pyramid has five faces.
Challenge the class to give as many reasons as they can to explain why each object is really the odd man out.
sphere | cylinder | cuboid (box) | square pyramid |
rolls no matter how you put it down | has curved and flat faces | has 6 faces | has 5 faces |
any diameter is an axis of rotational symmetry | has circular faces | has 4 rectangular faces | has 4 triangular faces |
could play netball with it | any cross-section parallel to a face is a circle | any cross-section parallel to a rectangular face is a rectangle | has a vertex where 4 faces meet |
… | has two edges but no vertices | has 12 edges | has 8 edges |
… | … | has 8 vertices | … |
Add to the table as different properties of the given objects emerge and as further shapes are explored and compared.
Printed from https://meaningfulmaths.nt.edu.au/mmws/nz/resource/odd-thing-out at 8:55pm on the 26th February 2024