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This downloadable interactive eBook file provides you with a zip file including a PC and MAC installer, which guides you through the installation process. This file is approximately 25 MB, so download times vary depending on your internet connection and computer speed. Download step-by-step instructions. What makes a parallel line sad? Why is nine a magic number? How can a...

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This downloadable interactive eBook file provides you with a zip file including a PC and MAC installer, which guides you through the installation process. This file is approximately 65 MB, so download times vary depending on your internet connection and computer speed. Download step-by-step instructions. Teresa's grandfather tells her that time travel is possible. Can he be serious? How can...

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This downloadable interactive eBook file provides you with a zip file including a PC and MAC installer, which guides you through the installation process. This file is approximately 64 MB, so download times vary depending on your internet connection and computer speed. Download step-by-step instructions. Without Earth's magnetic field, it would be impossible for us to live. So what creates...

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