Discussion

A circular path of 13 m radius has marginal walk 2 m wide all round it. Find the cost of leveling the walk at 25p per m²?

Answer: C

The walk lies outside the path, so it is the ring between radius 13 m and radius 15 m.

\[ A = \pi\left(15^{2} - 13^{2}\right) = \frac{22}{7}(225 - 169) = \frac{22}{7} \times 56 \]

\[ = 22 \times 8 = 176 \text{ m}^{2} \]

At 25 paise, that is a quarter of a rupee per square metre:

\[ \text{cost} = 176 \times 0.25 = \text{Rs. } 44 \]

Reading 25p as Rs. 25 would inflate the answer a hundredfold.

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