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KK.1 Solve word problems with area, perimeter, and side length

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What is perimeter?

Perimeter is the distance around a shape. You find it by adding the lengths of all the sides.

How to Identify:
  • Look for the word “around” or “border.”
  • Check if the problem asks for the total distance around a figure.
  • Be ready to add all the side lengths.
Example:
  • A rectangle has sides of 5 cm and 3 cm. Perimeter = 5 + 3 + 5 + 3 = 16 cm.
Note

When all sides are the same length (like in a square), you can multiply one side by 4.

What is area?

Area is the amount of space inside a shape. You find it by multiplying the length by the width (for rectangles and squares).

How to Identify:
  • Look for words like “cover,” “inside,” or “space.”
  • Check if the problem asks how many square units fit inside a figure.
  • Be ready to multiply length × width.
Example:
  • A rectangle is 6 m long and 4 m wide. Area = 6 × 4 = 24 square meters.
Note

Always label area with “square units” (like cm², m², or in²).

How are side lengths used?

Sometimes a problem gives only part of the side lengths. You may need to use addition, subtraction, or multiplication to find missing sides before solving for perimeter or area.

How to Identify:
  • Look for missing sides in a diagram.
  • See if opposite sides are equal in rectangles and squares.
  • Use the given information to calculate the missing length.
Example:
  • A rectangle has a length of 8 cm and a perimeter of 26 cm. To find the width: 26 − (8 + 8) = 10, then 10 ÷ 2 = 5 cm.
Note

In rectangles, opposite sides are always equal. Use this fact to solve for missing side lengths.

Solving word problems with area and perimeter

Word problems connect math to real-life situations. You may need to decide whether the problem is asking about perimeter (around) or area (inside).

How to Identify:
  • Underline key words: “around,” “fence,” “border” → perimeter.
  • Underline key words: “cover,” “paint,” “floor,” “inside” → area.
  • Draw a picture to organize the information.
Example:
  • Maria wants to put a fence around her rectangular garden that is 9 ft long and 7 ft wide. Perimeter = 9 + 7 + 9 + 7 = 32 ft.
  • A rug is 5 ft long and 4 ft wide. How much floor does it cover? Area = 5 × 4 = 20 square feet.
Note

Always reread the question to make sure you solved for the right thing—area or perimeter.

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