Find perimeter when given side lengths

The  exercise appears under the 3rd grade (U.S.) Math Mission. This exercise introduces users to basic perimeter using addition and multiplication.

Types of Problems
There are three types of problems in this exercise:
 * 1) Finding the perimeter of shapes with given values: In this type of problem, students are given a shape (Eg: A triangle) with given side lengths and asked to find the perimeter.
 * 2) Finding the perimeter of complex shapes: In this type of problem, students are given a complex shape and a value for each square and asked to find the perimeter.
 * 3) Identify expressions of perimeter: This problem has a polygon drawn and several numerical expressions below it. The student is asked to identify all the expressions that can be used to correctly find the perimeter of the shape.

Strategies
Knowing that perimeter is the sum of the lengths of all sides of a polygon is the only knowledge needed to do this problem correctly. Careful reading is needed on some problems.
 * 1) Perimeter is the sum of the lengths of all sides of a polygon.
 * 2) The numbers on this exercise are fairly small so it can be faster to perform the arithmetic mentally if possible.

Real-life Applications

 * 1) Perimeter is used for building a swimming pool. The owner of the pool wants to maximize the area within constraints of property and minimize the amount of digging and concrete, etc. that goes into the project. Yet the perimeter also defines length that is used for swimming races.