A cone has a circular base and a pointed top. A "perfect" cone is made from a half circle of paper (or any flexible material). A cone made from a half circle will have a bottom diameter equal to the radius of the circle, and the length of the side will be the same as the radius of the circle. You can make an adjustable cone out of a full circle of paper with a single cut through the radius of the circle.

- Skill level:
- Easy

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### Things you need

- Paper
- Circular object or pencil compass
- Scissors
- Tape or glue
- Ruler (optional)

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## Instructions

- 1
Trace a circle onto the flexible material (paper is good for starters). You can use any circular object as a guide, such as a salad plate or DVD, or use a pencil compass for exact measurements.

- 2
Cut out the circle with a pair of scissors.

- 3
Find the centre of the circle. Fold the circle in half but do not crease the fold. Match the circular outside edges as perfectly as possible. You are holding the circle in a shape like the shell of a taco. Estimate the approximate centre of the folded (but not creased) edge. Pinch the centre with your fingers to make a small crease only in that area. Unfold the circle, turn it 90 degrees and refold the circle, again not creasing the fold but making another taco shape. Repeat the estimation of the centre of the folded edge and make another pinch there. Unfold the circle. The intersection of the fold marks should be the centre of the circle.

- 4
Draw a line from any point on the outside of the circle to the midpoint. Cut along this line from the outside to the midpoint using the scissors.

- 5
Slide one of the cut edges under the other edge. The more you slide the edges, the steeper the cone becomes. You can make any type of cone with this slit disk. Tape or glue when you have the desired dimensions for your cone. Trim excess paper off the inside or outside edge before gluing or taping as desired.

## Making Adjustable Cones

- 1
Measure the circle. If you need a cone with a particular diameter at the base, start with a circle that has a radius equal to that diameter. For instance, for a 2-inch diameter cone, start with a circle with a radius of 2 inches (the circle's diameter is 4 inches).

- 2
Find the centre using Step 3 in Section 1. If you used a compass to make the circle, find the indentation point that the compass tip made when you drew the circle. This is the centre.

- 3
Lay a ruler across the circle so the edge of the ruler is against the centre of the circle. Draw a line across the circle so you have two half circles.

- 4
Keeping the ruler on the centre point, move the top end of the ruler about 1/2 inch along the circumference of the circle. Draw a line from this point to the centre point. This creates a tab, like a small slice of pie.

- 5
Cut out the half circle with the added tab or slice. Glue or tape the cone together with this tab slid under the other side of the half circle.