If 2/3 of the air in a tank is removed with each stroke of a vacuum pump, how many strokes does it take before less than 1% of the original amount of air in the tank remains?	Choose the correct choice from the following.
A) 2	B) 3	C) 4	D) 5	E) 6
My approach is to find more or less good number and plug in. Lets take 90 as the total volume of an air, and the question asks after how many stokes there will be less than 0,9 air in a tank, if each stroke takes 2/3 of an air.   So after he1 strokethe volume will be 30 (90-60=30), and so on   2 stroke- 30-20=10   3 stroke- 10-6,7=3,3   4 stroke- 3,3-2,2=1,1   5 stroke- 1,1 - minus something that gets us less than 0,9 for sure. so the answer is: after 5 strokes there will be less than 1% of air left in a tank. Option5.
<result>D</result>
If 2/3 of the air in a tank is removed with each stroke of a vacuum pump, how many strokes does it take before less than 1% of the original amount of air in the tank remains?