Estimate through calculation the loc of octane. assume the lfl is 1.28 vol. %. [16b] when purging an octane tank it is desired to lower the oxygen concentration 40% below the loc. the initial oxygen concentration in the tank is 30 volume percent. a vacuum system capable of 290 mm hg abs. is available. assuming atmospheric pressure is 1 atm and the inert contains 1000 ppm oxygen. how many purging cycles does it take?

Mass is the amount of matter in an object.  weight is the measurement of the pull of gravity on an object.  say for example, you travel to the moon which has a different gravitational field compared to the gravitational field of earth. (gravitational fields: earth = 1, moon = 0.165)  now when you are on the moon, the pull of gravity on you is different than on the earth. and as weight is the measurement of the pull of gravity on an object, that means yes, your weight can and will change on the moon.  however, on the moon, on earth or even on jupiter, the amount of mass inside of you remains the same. meaning your physical mass remains constant.  in conclusion it is possible for your weight to change as your mass remains constant. 

Is a logical series of steps

4.49 gramshope that fren : )