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## Estimating Surface Area

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**Estimating Surface Area**The art of math…**You can’t always get an exact answer when looking for the**surface area of a complex 3-D shape We use estimation methods to get an approximate answer We will demonstrate this with a cone (even though there is a formula available) Estimating the Surface Area of 3-D Objects Cone**Model Your Shape**• Simple shapes can be used to estimate the surface area of more complicated 3-D objects • What shape do you think we should use?**This will provide an estimate by using a shape we are more**familiar with If we only use the sides of the cylinder will this is an over or under estimate? Estimating with cylinders**You can see from the “net” that the cone had more**surface area than the cylinders What happens to our estimate if we use larger Cylinders? It was an underestimate**The cylinders are obviously larger than the cone**Do you think this is more accurate? How do you know? Over Estimating**What if we averaged our results? Or tried cylinders a little**smaller than these but bigger than the first set? What else could we try? Over Estimating**This is still an underestimate, BUT it is a better model for**the cone This gives a much closer estimate than our first approach What happens if you increase the number of cylinders?**There is a formula for surface area of a cone**Is there a formula for this shape? What shape should we use to calculate the surface area of this one? More Complicated Shapes**Notice that we don’t need all if the area, it was an over**estimate!**More complicated shapes**• What do you think we should do?**This looks pretty good…**• Don’t forget, not all the surface area of the boxes needs to be counted.