A moon phase is the shape of moon's sunlit portion as seen from Earth. There are a total of eight moon phases: new, waxing crescent, first quarter, waxing gibbous, full, waning gibbous, third quarter, and waning crescent. These phases repeat every 29.5 days. Khan Academy is a nonprofit organization with the mission of providing a free, world-class education for anyone, anywhere. We offer quizzes, questions, instructional videos, and articles on a range of academic subjects, including math, biology, chemistry, physics, history, economics, finance, grammar, preschool learning, and more. We provide teachers with tools and data so they can help their students develop the skills, habits, and mindsets for success in school and beyond. Khan Academy has been translated into dozens of languages, and 15 million people around the globe learn on Khan Academy every month. As a 501(c)(3) nonprofit organization, we would love your help! Donate or volunteer today! Donate here: https://www.khanacademy.org/donate Volunteer here: https://www.khanacademy.org/contribute ... https://www.youtube.com/watch?v=f592IgRzq2E Note: All Khan Academy content is available for free at (www.khanacademy.org)

We're flipping the last video on its head and doing the opposite. This time we give you the graph and ask you to express it as an equation. Practice this lesson yourself on KhanAcademy.org right now: https://www.khanacademy.org/math/algebra/introduction-to-algebra/feel-for-equations-and-inequalit/e/dependent-and-independent-variables?utm_source=YT&utm_medium=Desc&utm_campaign=AlgebraI Watch the next lesson: https://www.khanacademy.org/math/algebra/introduction-to-algebra/units-algebra/v/can-a-squirrel-avoid-getting-run-over?utm_source=YT&utm_medium=Desc&utm_campaign=AlgebraI Missed the previous lesson? https://www.khanacademy.org/math/algebra/introduction-to-algebra/feel-for-equations-and-inequalit/v/dependent-and-independent-variables-exercise-example-2?utm_source=YT&utm_medium=Desc&utm_campaign=AlgebraI ... https://www.youtube.com/watch?v=3ACF7L-7Vsg Note: All Khan Academy content is available for free at (www.khanacademy.org)

Water in a pipe. Watch the next lesson: https://www.khanacademy.org/math/ap-calculus-ab/ab-solved-exams/ab-solved-exams-2015/v/2015-ap-calculus-abbc-1c?utm_source=YT&utm_medium=Desc&utm_campaign=APCalculusAB Missed the previous lesson? https://www.khanacademy.org/math/ap-calculus-ab/ab-solved-exams/ab-solved-exams-2017/v/2017-ap-calculus-abbc-4c?utm_source=YT&utm_medium=Desc&utm_campaign=APCalculusAB AP Calculus AB on Khan Academy: Bill Scott uses Khan Academy to teach AP Calculus at Phillips Academy in Andover, Massachusetts, and heÕs part of the teaching team that helped develop Khan AcademyÕs AP lessons. Phillips Academy was one of the first schools to teach AP nearly 60 years ago. About Khan Academy: Khan Academy is a nonprofit with a mission to provide a free, world-class education for anyone, anywhere. We believe learners of all ages should have unlimited access to free educational content they can master at their own pace. We use intelligent software, deep data analytics and intuitive user interfaces to help students and teachers around the world. Our resources cover preschool through early college education, including math, biology, chemistry, physics, economics, finance, history, grammar and more. We offer free personalized SAT test prep in partnership with the test developer, the College Board. Khan Academy has been translated into dozens of languages, and 100 million people use our platform worldwide every year. For more information, visit www.khanacademy.org, join us on Facebook or follow us on Twitter at @khanacademy. And remember, you can learn anything. ... https://www.youtube.com/watch?v=ZsxMPW083mI Note: All Khan Academy content is available for free at (www.khanacademy.org)

Use the distributive property to understand the products of negative numbers. Practice this lesson yourself on KhanAcademy.org right now: https://www.khanacademy.org/math/arithmetic/absolute-value/mult_div_negatives/e/multiplying_and_dividing_negative_numbers?utm_source=YT&utm_medium=Desc&utm_campaign=PreAlgebra Watch the next lesson: https://www.khanacademy.org/math/arithmetic/absolute-value/mult_div_negatives/v/why-a-negative-times-a-negative-makes-intuitive-sense?utm_source=YT&utm_medium=Desc&utm_campaign=PreAlgebra Missed the previous lesson? https://www.khanacademy.org/math/arithmetic/absolute-value/mult_div_negatives/v/multiplying-positive-and-negative-numbers?utm_source=YT&utm_medium=Desc&utm_campaign=PreAlgebra Pre-Algebra on Khan Academy: No way, this isn't your run of the mill arithmetic. This is Pre-algebra. You're about to play with the professionals. Think of pre-algebra as a runway. You're the airplane and algebra is your sunny vacation destination. Without the runway you're not going anywhere. Seriously, the foundation for all higher mathematics is laid with many of the concepts that we will introduce to you here: negative numbers, absolute value, factors, multiples, decimals, and fractions to name a few. So buckle up and move your seat into the upright position. We're about to take off! ... https://www.youtube.com/watch?v=rK4sXm_MPWo Note: All Khan Academy content is available for free at (www.khanacademy.org)