If 1/2 of the air in a tank is removed with each stroke of a vacuum pump, what fraction of the original amount of air has been removed after 5 strokes ?\nOptions:\n(A) 31/32\n(B) 7/8\n(C) 1/4\n(D) 1/8\n(E) 1/16 Hmmm, my stream of consciousness:
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Left After 1st stroke = 1/2\nLeft After 2nd stroke = 1/2 * 1/2 = 1/4\nLeft After 3rd stroke = 1/2 * 1/4 = 1/8\nLeft After 4th stroke = 1/2 * 1/8 = 1/16\nLeft After 5th stroke = 1/2 * 1/16 = 1/32\nSo removed = 1- 1/32 = 31/32 So, the answer is (A).
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