Question 1061998
Part 1:
42*3 = 126mm is the length of the box
The sides are 42 x 42
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Part 2:
42*Pi is the circumference of the cylinder and 126 is the height (or length)
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Part 3 - Exterior surfaces only, if you need external and internal multiply times 2.
Box:
The box has 4 sides and 2 ends:
Sides (4 sides): 4(126*42) = 
Ends (2 ends): 2(42*42) = 
Multiply and add the products to get the total area of the rectangular prism
Cylinder:
(42*Pi)*126 outside surface of the cylinder (like I said, if you need internal and external just multiply times 2)
Ends (2 ends): 2*[Pi*(42/2)^2] = 2*[Pi*21^2] add this to the area of the cylinder above. Again, if you need the surface of both sides you need to multiply the result times 2.