Question 830167
Not being sure if this was intended as a Scientific Notation problem, or a Continued Proportion Unit Conversion problem, I will start with assigning variables.



v = 3.60 mL water sample
g = 4.00*10^(-10) grams Gold
C = 1.50*10^21 Liters water in all earth
m = 19.64 dollars per gram, worth rate of Gold


A unit conversion will be needed, arbitrary convenience to change v into its value in Liters.  How about reassigning v, right now before continuing?


Reassigning v to its Liter value:

{{{v = 3.60*mL((1*L)/(1000*mL))=0.00360}}} Liters water sample
{{{g = 4.00*10^(-10)}}} grams Gold in the v amount of sample
{{{C = 1.50*10^21}}} Liters water in all earth
{{{m = 19.64}}} dollars per gram, worth rate of Gold


Decide which number to start.  Look AT the question.  You want how much Gold in THE WORLDS OCEANS.  You want to convert C, the amount of all the world's oceans, into MONEY'S-WORTH of Gold.  You want some number of DOLLARS as a result.


I will show the numbers, all together, BUT the units all AFTER the number expression:


{{{C(g/v)m*(L(grams/L)(dollars/gram))}}}
You should examine clearly to understand that this is in units of Dollars.
The numbers part is {{{highlight(C(g/v)m)}}}.
-
Fill-in the values for the variables:
{{{(1.50*10^21)((4.00*10^(-10))/(3.60*10^(-3)))19.64}}} dollars



The computation was not performed here.  If you have trouble with this, then say, and I will provide some computation steps.