The area of a square and the area of a rectangle are equal. If the side of the square is 40 cm and the length of the rectangle is 64 cm, find the perimeter of the rectangle in cm, assuming both shapes have exactly the same area.

Difficulty: Medium

Correct Answer: 178 cm

Explanation:


Introduction / Context:
This problem tests the relationship between area and perimeter across different shapes. You are told that a square and a rectangle have the same area. The square’s side gives you its area directly. Then, using the rectangle’s length, you can compute its breadth from area = length * breadth. Finally, apply the rectangle perimeter formula 2 * (length + breadth).


Given Data / Assumptions:

  • Side of square = 40 cm
  • Area of square = side * side
  • Rectangle length = 64 cm
  • Areas are equal, so rectangle area = square area
  • Perimeter of rectangle = 2 * (length + breadth)


Concept / Approach:
Compute square area. Use it as rectangle area. Find breadth = area / length. Then compute perimeter from length and breadth.


Step-by-Step Solution:

Step 1: Area of square = 40 * 40 = 1600 sq cm Step 2: Rectangle area = 1600 sq cm (equal areas) Step 3: Breadth of rectangle = area / length = 1600 / 64 = 25 cm Step 4: Perimeter = 2 * (64 + 25) = 2 * 89 = 178 cm


Verification / Alternative check:
Check area consistency: 64 * 25 = 1600 sq cm, which matches the square’s area. Since the area match is correct, the perimeter calculation using those dimensions is valid.


Why Other Options Are Wrong:

187 cm and 194 cm: would imply a larger breadth than 25 cm for the same length and area. 149 cm: would imply a smaller breadth, which would reduce area below 1600 sq cm. 168 cm: corresponds to (64 + 20) * 2, but breadth 20 would give area 1280, not 1600.


Common Pitfalls:
Common mistakes include using perimeter formulas for area, mixing up square side with rectangle length, or calculating breadth as 64/1600 instead of 1600/64. Also, always keep units consistent in cm throughout the calculation.


Final Answer:
178 cm

More Questions from Area

Discussion & Comments

No comments yet. Be the first to comment!
Join Discussion