How to Find the Basic Perimeter Math Problems
The perimeter is the measure of the distance around an object or a shape. If all the sides of the object are straight, this is fairly simple to measure or compute. If the rim of the object is curved, it is harder to measure and requires a different set of skills. If the object is complex, the perimeter is calculated by mentally breaking up the object into simple shapes, calculating the measurement of each simple shape and adding them together.
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Instructions
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Measure one side if your object is "regular." Regular is a common object in which all the sides are the same length. Regular objects include squares, equilateral triangles and pentagons. Measure one side and multiply the number by the number of sides. Some objects are "semi-regular" in that opposite sides are equal -- such as rectangles and parallelograms. For semi-regular objects, measure only one of each of the parallel sides and double it. The "M" keys on your calculator make this kind of thing easier. Start by clearing memory with the "MC" button. Each side that you measure can be accumulated into memory with the "M+" key. The "M+" key adds the current calculator screen to the memory.
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Compute the perimeter of circles or parts of circles. The perimeter of a circle is also called the circumference. It is found by multiplying the diameter by pi, which is roughly 3.14159265. An easy method to find the diameter of a circle is to put something with a right angle -- like a sheet of paper -- over the circle in such a way that the right angle just touches some point on the circle and the straight sides cut the circle in two other places. Measure the distance between the two places where straight sides cut the circle -- this is the diameter. Multiply by pi to get the perimeter.
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Calculate the perimeters of more complex shapes or objects by breaking the perimeters into small shapes -- each of which is either a straight line or a circle. Find each section's contribution and add them together to get the total perimeter. If this proves too difficult, or the shapes are neither straight or circular, lay a piece of string along the perimeter of the object. Then cut the string to fit exactly -- the string is the duplication of the perimeter. Take the string to a flat surface, straighten it out and measure it.
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Tips & Warnings
Measure each distance several times -- it is easy to make a mistake while measuring an object. If you keep getting the same results, your results are more secure.
It is not always easy to tell if a corner is exactly square or if a shape is exactly a circle. When in doubt, use the string method.
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