Boulder, Cobble, Pebble, Sand, Silt, Clay
From the law of sines, we have

where
is the leg we're interested in,
is the hypothenuse,
is the angle opposite to
, and
is the angle between
and
.
So, in the first case, we can use

And in the second excercise, we use

The missing length is 12km (i never promised anything xd)
We know it begins at 100. If we use a*b^t, then 100 is our a. 100*b^t. We can now divide 480 by 100. This is 4.8. 4.8 is b. f(t) = 100(4.8)^t