How to Find Dimensions in Geometric Shapes

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Students need to learn many key math skills throughout their schooling. Among those skills is finding dimensions of geometric shapes. To master this skill, you will need to follow some basic rules and equations while practicing formulas. To complete this task, you also need to look for the right information, and perform basic problem solving.

Dimensions of a Square

    Locate the area or perimeter of the square. The area or perimeter of the square has to be provided to find its dimensions. For example, suppose the area of a square is 25 square feet. Write down the area equation for a square: A = t^2 where "A" stands for the area and "t" stands one of the side lengths. Remember you only have to find one dimension since the square has four equal sides.

    Solve the area equation. It will look like this 25 = t^2. You have to isolate "t" to find the dimension of the square. Do this by taking the square root of 25; this will cancel out the square sign on the right side of the equation. The answer for the square root will be 5. The final answer is 5 = t, so each dimension of the square is 5 feet.

    Find the dimensions of the square using the perimeter. For this example, the perimeter of the square will be 20 feet. Write down the perimeter equation for a square: P = 4t where "P" stands for perimeter and "t" stands for the side dimension.

    Solve the perimeter equation. It will look like this: 20 = 4t. Divide each side of the equation by 4, and write down the answer for both sides: 5 = t. The final answer is t = 5, which means the dimensions of the square are 5 feet each.

Dimensions for a Rectangle

    Search for the area or perimeter of the rectangle. The area or perimeter of the rectangle and either the length or the width has to be provided to find its dimensions. For this example, use 30 square feet as the area, and 6 feet as the width. Write down the area equation: A = L * W where "A" stands for the area, "L" stands for the length and "W" stands for the width of a rectangle.

    Solve the area equation: 30 = L * 6. Divide both sides of the equation by 6, and write down the answer. It will look like this: 5 = L. Keep in mind a rectangle has two equal lengths and two equal widths. The final answer is the dimensions of the rectangle are 6 feet for each of the lengths and 5 feet for each of the widths.

    Find the dimensions of the rectangle using the perimeter. For this example, suppose the perimeter is 22 feet and the length is 5 feet. Write down the perimeter equation for a rectangle: P = 2L + 2W where "P" stands for perimeter, "L" stands for the length and "W" stands for the width.

    Fill in the perimeter equation. It will look like this: 22 = 2(5) + 2W. Multiply the "2 x 5" on the right side of the equation, and you will now have 22 = 10 + 2W. Subtract 10 from each side of the equation to obtain 12 = 2W. Divide both sides of the equation by 2 to find out what the width is. The final answer is W = 6. So the dimensions of the rectangle are 5 feet for each of the lengths and 6 feet for each of the widths.

    Tips

    • Make sure to use the area and perimeter equation of each specific geometric shape when solving for the dimensions.

References

About the Author

Will Samuel started writing in 2006. Prior to writing for eHow, Samuel wrote performance plans for Teletech Holdings and Aditya Birla Minacs. He is a finance and marketing student at Saint Mary's University.

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