Geometry

Question Analysis
This question combines the calculation of the surface area of a sphere with unit conversion.
The main focus is on correctly converting the diameter from inches to feet, calculating the surface area, and then determining the number of varnish cans required.

Key Concept Explanation
First, convert the linear unit from inches to feet using the conversion factor 1 foot = 12 inches.
Then, use the formula for the surface area of a sphere , where is the radius.
Finally, divide the total surface area by the area covered by one can of varnish to find the number of cans.

Step - by - Step Solution
Convert the diameter from inches to feet: inches feet, so the radius feet.
Calculate the surface area: ,

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