Johanna

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2. General Khan Academy Questions
3. Mastery In a Course

Yes, you can get to 100 percent mastery in a course without doing the course challenge. As you suggest, it depends on if you mastered the skills or not. To achieve mastery in those skills, though, ...

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3. Re acceleration formula

Both of those equations are very widely accepted as correct. What do you mean by “the v0t is not half”/ why would that make one equation wrong? Sorry about the late response.

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3. Chemistry of life - carbon-14 dating question

If you want, you might have better luck getting an answer if you ask this in the questions section under that article.