Question 597798
12% of 6.6 billion is 0.12*6.6 = 0.792


So 12% of 6.6 billion is 792 million.


Therefore, 792 million people have this disease.


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Now we need to convert 50 gallons into milliliters. 


It turns out that 


1 gallon = 3785.41178 mL


Note: this is something you either memorize or you have to look up.


Multiply both sides by 50 to get


50*1 gallon = 50*3785.41178 mL


50 gallon = 189270.589 mL


So 50 gallons converts to 189,270.589 mL. Round down to get 189,270


This means that one 50 gallon vat can cure 189,270 people.


Now divide 792 million (7.92 x 10^8) by 189,270 (1.8927 x 10^5) to get



(7.92 x 10^8)/(1.8927 x 10^5)


(7.92/1.8927) x ((10^8)/(10^5))


4.18449833571089 x 10^(8-5)


4.18449833571089 x 10^3



and then convert this answer to standard decimal notation to get 4,184.4983357108


and then round up to get the final answer of <font color="red">4,185</font> vats