Q: 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 6 strokes ?\nOptions:\n(A) 63/64\n(B) 7/8\n(C) 1/4\n(D) 1/8\n(E) 1/16 Let's give some random thoughts before answering.
User
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\nLeft After 6th stroke = 1/2 * 1/32 = 1/64\nSo removed = 1- 1/64 = 63/64
Therefore, the answer is (A).
Assistant