scale
2 times a 6 inch ruler
Foot
A ruler.
30cm is about 12 inches or 1 foot in length
A ruler is 12 inches long.
my penis is
The shape of the object is missing from the question which, therefore, cannot be answered.
12 yards is 432 inches.
12 inches
To convert inches to square inches you need to know 2 different dimensions of an object. The 2 dimensions have to be in inches or converted into inches. Here is an example: The front of an object is 1 foot tall by 8 inches wide, what is the objects area in sq. inches. Solution: Height is 1 foot or 12 inches and the width of the object is 8 inches. 12 inches x 8 inches = 96 sq. inches.
To the nearest 12 inches it is 12 inches long. To the nearest 14 or 18 inches, it is 0 inches long.
A diameter is a property of circular objects. "12 inches" is not a circular object and so cannot have a diameter.
a board
3
It normally refers to a cuboid (a brick shaped object) that is 16 inches long, 14 inches wide and 12 inches deep. However, it could refer any shape which would just fit into a cuboid of the above size. Any of the measures could be referred to as "long", "wide" or "high" but it is customary to refer to the biggest side as "long".