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# Slicing and cutting problems

### Purpose:

The purpose of this activity is to help your child to make common solid (three-dimensional) shapes and make paper/cardboard patterns for these, and to correctly identify prisms.

Your child is learning to make paper or cardboard patterns (nets) for common three-dimensional shapes, and to identify prisms by their features.

### What you need:

• Play dough - click for recipe (PDF, 325KB)
• A plastic knife, or ‘safe’ kitchen knife
• Spare paper or cardboard
• Pencil, ruler and eraser
• Scissors
• Cellotape or glue

### What to do:

• Have your child use the dough to make and name a cube, a cylinder, a sphere, a cuboid (long cube or rectangular prism), a square based pyramid, a cone and a triangular prism.

• Have your child talk to you about the distinguishing features of each shape, for example "The square based pyramid has 5 vertices (corners where 3 edges meet), 8 edges (where 2 ‘sides’ or faces meet), and 5 faces of which one is a square and 4 are triangles."

• Have your child chose some of the shapes with straight edges, and using paper or card, make and cut a pattern for this shape. They should include tabs on their pattern so the shape can be folded and glued to make a three dimensional model. For example:

Have your child put their play dough shapes in the fridge while they cut out and glue/tape their paper/cardboard shapes together. Chilling the dough shapes will make them firmer and this will make the next task more successful.

• Now say, “I want you to slice at least twice through each play dough shape. But before you do, I want you to predict which shapes will have slices that are all the same size and shape, and which ones will have slices that are different sizes or shapes.”

• Have them make their prediction and then have them slice through their play dough shapes to see if their predictions are correct.
NB. When a prism is sliced through, its slices are the same size shape, like this:

If you slice through a shape that is not a prism, eg, a pyramid, the slices will change shape and size.
So, a prism is a solid object that has two identical ends and all flat sides. The cross section is the same all along its length.

• Talk together about what has happened and together agree which shapes are prisms.

### What to expect your child to do:

• Make and name common solid three-dimensional shapes.
• Make paper or cardboard patterns (nets) for common three-dimensional shapes.
• Identify features of prisms.

### Related Māori vocab:

 play dough poikere shape āhua round porotaka straight torotika sharp, pointy koi, whakakoikoi curvy, bendy kōpiko flat papatahi cone koeko cube mataono rite corner, vertice kokonga edge tapa surface/face mata cone koeko cylinder rango sphere poi rectangular prism poro tapawhā hāngai pyramid koeko tapawhā rite triangular prism poro tapatoru net (of a 3 dimensional shape) raumata