
unit conversion
2a)Dr. Hole describes a block of granite that is 1 cubic foot and weighs
175 lbs. Determine the density of the granite in g per cubic centimeters
(remember that 1 foot = 12 inches, 1 inch = 2.54 cm, 1 lb = 454 g)
2b) Extra credit. Imagine that Dr. Hole's block of granite has turned into
a sandy loam soil with 60% sand, 30% silt and 10% clay. How many soil
particles are contained in 1 cubic cm of this soil (bulk density = 1.4
g/cm3). Assume (as mentioned in the article) that 1 g of sand contains 1000
particles, 1 g of silt contains 6 million particles and 1 g of clay
contains 90 billion particles.
If you can get me started I would greatly appreciate it!

Recall that density is defined as being the amount of mass in a certain volume.
Or:
$\displaystyle d = \frac{m}{v}$
So we can say that:
$\displaystyle d = \frac {165 lbs.}{1 ft^3}$
Now we need to convert into the units that were asked for:
$\displaystyle \frac {165 lbs.}{1 ft^3} \cdot \frac {1 ft}{12 in.} \cdot \frac {1 in.}{2.54 cm} \cdot \frac {454 g}{1 lb.} = ?$
Just multiply out and you have your answer.
