Math question: Find the radius of a circle if its equation is x^2 + y^2 = 16. (
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Find the length of the major axis of an ellipse with a vertical major axis, when the coordinates of the foci are (0, ±9) and the distance between a focus and a vertex is 15.
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What is the probability of getting exactly 4 heads in 10 coin flips if the probability of heads is 0.5?