How many different ways can 4 students line up for a photo?
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Math question: In a triangle ABC, if angle B = 90 degrees, and circle O with center C and radius r is inscribed in the triangle, what is the length of AB?
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What is the median of the following data set? {15, 19, 21, 23, 26, 30, 34, 38, 40, 42}