The planet Jupiter is more than 300 times as massive as earth, so it
might seem that a body on the surface of Jupiter would weigh 300 times
as much as on earth. But really a body would scarcely weigh 3 times
as much on the surface of Jupiter as it would on the surface of earth.
Can you think of an explanation for why this is so? (Hint: Think of
the equation for gravitational force?)
I found this problem, with its answer, on a high school website:
"10. The planet Jupiter is more than 300 times as massive as Earth, so
it might seem that a body on the surface of Jupiter would weigh 300
times as much as on Earth. But it so happens a body would scarcely
weigh three times as much on the surface of Jupiter as it would on the
surface of the Earth. Explain why this is so."
Glenbrook High School: Newton's Law of Universal Gravitation
http://www.glenbrook.k12.il.us/gbssci/phys/Class/circles/u6l3c.html
"The effect of the greater mass of Jupiter is partly offset by the
fact that the radius of Jupiter is larger. An object on Jupiter's
surface is 10X farther from Jupiter's center than it would be if on
Earth's surface. So the 300-fold increase in force (due to the greater
mass) must be divided by 100 since the distance is 10X greater."
Glenbrook High School: Check Your Understanding Answer
http://www.glenbrook.k12.il.us/gbssci/phys/Class/circles/cyuAnswers/l3cq10.html
Here's another way to put it:
"The gravitational force on a body depends on mass and distance. If
Jupiter were the same size as the Earth objects would weigh 300 times
more at the surface of Jupiter, because Jupiter is 300 times more
massive. But Jupiter is also much bigger so the actual weight of
objects on Jupiter?s surface would only be 3 times bigger than the
weight on Earth."
Hartnell College: Physics 10 Homework Solutions
http://www.hartnell.cc.ca.us/physics/physics10/Solutions2.pdf
And an even shorter answer:
"7) The planet Jupiter is about 300 times as massive as the earth, yet
on its surface you would weigh only about 3 times as much. This is
because...
Jupiter's radius is 10 times the earth's radius."
Drake University: Sample Exam One
http://www.drake.edu/artsci/physics/Sample_Exam_One.html
My Google search strategy:
Google Web Search: "300 times" jupiter earth weigh "3 OR three times"
://www.google.com/search?hl=en&q=%22300+times%22+jupiter+earth+weigh+%223+OR+three+times%22
I hope this is helpful.
Best regards,
pinkfreud
 Walking/Running Puppy - Advise needed
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equation for gravitational force