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 ?
Options:
(A) 63/64
(B) 7/8
(C) 1/4
(D) 1/8
(E) 1/16 Now, let's think a bit. Some random thoughts:
Left After 1st stroke = 1/2
Left After 2nd stroke = 1/2 * 1/2 = 1/4
Left After 3rd stroke = 1/2 * 1/4 = 1/8
Left After 4th stroke = 1/2 * 1/8 = 1/16
Left After 5th stroke = 1/2 * 1/16 = 1/32
Left After 6th stroke = 1/2 * 1/32 = 1/64
So removed = 1- 1/64 = 63/64
The final answer: (A).