How does weight change as the gravitational acceleration changes and why?

Answer

The correct formula for weight is F = m*g where g is the gravitational acceleration.

All over the earth's surface, g is slightly different. The mass does not change no matter where you are. We should be measuring out weights in Newtons, not in kg. So the unit of weight in the metric system is 9.8 about * mass in kg.

Stop reading. This is your answer.

Notes

It was hard enough to get people to change over to kg never mind newtons. Canada, which is on the metric system, still gives the price of food in pounds. Or if not, in grams if the container is small enough.

Cashews cost 19$ Canadian per 906 grams which is roughly 2 pounds.

Oranges are $1.27 a pound and that is the way they are listed in Walmart.

10 pounds of potatoes are 4.95 dollars.

I'm sure you get the point. We use kg for certain things and retain pounds for others.  

t = 1/400 h   ⇔ 0.0025 h ⇔ 9s ⇔ 0.15 m

any of the answers are correct.