Please help........this is not in the book?

In the famous Luray Caverns located in Luray, Virginia, stalactites are formed by a process of water depositing minerals in the form of a cone. The deposits accumulate at a rate of 1.00 cm3/300 years. Given that the density of the mineral is 1.20 g/cm3 and a particular stalactite has mass of 12 kg, calculate how old this stalactite is. Answer in years.Please help........this is not in the book?
This is a rate problem, but with some complications.



To solve a rate problem, you must first identify the rate, the time, and the functional equivalent of distance. Looking at the units is a big help in this. Rate units are usually most easily identified as one unit per another unit. The unit on top is the functional equivalent of distance, while the one on the bottom is the functional equivalent of time.



In this particular problem, the functional equivalent of distance is the accumulated mass, in grams, and the functional equivalent of time is indeed time, in years. However, the rate is given in units of volume per year, specifically



1.00 cm^3 / 300 yr



and must be converted to mass per year. This is accomplished by multiplying by the density, giving the rate of mineral accumulation, in grams per year, of



1.00 cm^3 / 300 yr * 1.20 g / cm^3 = 0.00400 g / yr



(the trailing zeroes are significant and imply a more precise number than 0.004 g / yr would.)



The basic rate problem is given by the equation



rt = D



but in this case, distance D is functionally replaced by mass, so the equation becomes



rt = m.



Plugging in the values we now have (after converting mass to grams and converting to scientific notation) we get



4.00e-3 g / yr * t yr = 1.20e4 g



or t = 1.20e4 / 4.00e-3 yr or 3.00e6 yr or 3.00 million years.Please help........this is not in the book?
3333 years



volume= 1.00 cm3/300 years.

v=0.003 cm3/year



Given that the density of the mineral is 1.20 g/cm3

and a particular stalactite has mass of 12 kg,



density=m/v



m=12000g

d=1.2g/cm3

v=0.003*years

1.2=12000/(0.003*years)



years=(12000/1.2)/0.003=3333 years