Difficulty: Easy
Correct Answer: Rs. 264
Explanation:
Introduction / Context:
This question requires converting area units, computing the radius from area, determining the circumference (fencing length), and finally multiplying by a cost rate per meter. Using π = 22/7 will keep numbers tidy if the area is chosen to be a perfect multiple.
Given Data / Assumptions:
Concept / Approach:
From A = πr^2, solve for r: r^2 = A/π. Then circumference C = 2πr gives the total fencing length. Multiply C by the rate to get cost.
Step-by-Step Solution:
r^2 = 138,600 / (22/7) = 138,600 * 7 / 22 = 44100r = √44100 = 210 mC = 2πr = 2*(22/7)*210 = 1320 mCost = 1320 * 0.20 = Rs 264
Verification / Alternative check:
Back-calc area from r = 210: A = (22/7)*210^2 = (22/7)*44,100 = 138,600 m^2 = 13.86 hectares — consistent.
Why Other Options Are Wrong:
Rs 277.20, Rs 324, and Rs 198 correspond to different circumferences not implied by A = 138,600 m^2 with π = 22/7. Only Rs 264 matches the exact computation.
Common Pitfalls:
Confusing perimeter with diameter, or forgetting the hectare-to-square-meter conversion, which is crucial here. Also, mixing paisa and rupee values (20 paisa = Rs 0.20) can cause arithmetic slips.
Final Answer:
Rs. 264
Discussion & Comments