Difficulty: Medium
Correct Answer: 120
Explanation:
Introduction / Context:This problem combines Pythagoras with perimeter relations to determine a rectangle’s area from diagonal and perimeter.
Given Data / Assumptions:
Concept / Approach:Use identity (a + b)^2 = a^2 + b^2 + 2ab to find ab, which equals the area for rectangles.
Step-by-Step Solution:
(a + b)^2 = 23^2 = 529.a^2 + b^2 = 289.So 529 = 289 + 2ab ⇒ 2ab = 240 ⇒ ab = 120.Area = a*b = 120 sq. cm.Verification / Alternative check:If a = 8 and b = 15, then diagonal √(64+225)=√289=17 and perimeter 2*(8+15)=46; area 120 checks out.
Why Other Options Are Wrong:110, 130, 140 do not satisfy both the diagonal and perimeter constraints simultaneously.
Common Pitfalls:Trying to solve for individual a and b first; area can be obtained directly from the identity without explicit a, b values.
Final Answer:120
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