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What’s the best size of disposable water bottle? Bottled water is one of the best-selling drinks on Earth. While disposable bottles offer a convenient way to stay hydrated, they also require a lot of plastic that can be harmful to the environment.

In this lesson, students use the volume and surface area of cylinders to compare disposable water bottles and consider environmentally-friendly ways to stay hydrated.

### Students will

• Use the formulas for volume of a cylinder and volume of a sphere to solve real-world problems.
• Model with geometry.
• Reason about the surface area of a real-world object. (No formulas required.)

### Before you begin

Students will compare and discuss surface areas of cylinders, but they do not need prior experience with these formulas.