If you are reading a book and you move twice as far away from the light source, how does the brightness at the new distance compare with that at the old distance? it is
a.
one-eighth as bright.
c.
one-half as bright.
b.
one-fourth as bright.
d.
twice as bright.

Brightness decreases with inverse proportion squared, so (let I stand for intensity and a be some proportionality constant):

If we increase our distance by a factor of 2 then

Thus the answer is b.

the skeletons of most mammals reach a certain size and then stop growing. however, many animals, including some mammals, keep growing throughout their lives. kangaroos, for example, just keep growing and growing until they die. also, the longer an animal lives the greater the chance it might catch some deadly disease.