standard_description: Recognize that a measure of center for a numerical data set summarizes all of its values with a single number, while a measure of variation describes how its values vary with a single number.
problem_activity: A tee-shirt store sells long sleeve (LS) and short sleeve (SS) tee-shirts. In the fall, they stock 4 LS tee-shirts for every 3 SS tee-shirts. In the spring, they stock only 2 LS tee-shirts for every 5 SS tee-shirts.
If the store stocks the same number of tee-shirts in the fall and in the spring, and there are 105 SS tee-shirts in the fall, how many SS tee-shirts does the store stock in the spring?


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