A circular park,

The diameter of a circular park = 42m

⇒ the radius of a circular park,

Width of path = 3.5m

⇒ radius of the park with path, R = 21 + 3.5 = 24.5m

∴ Area of path = Area of outer circle – Area of the inner circle

= πR² – πr²

= π (R² – r²)

= π (R – r)(R + r)

= 22 × 0.5 × 45.5

= 500.5 m²

Now, the cost of gravelling the path of 1m² = Rs 4

the cost of gravelling the path of 500.5m² = Rs 4×500.5

= Rs 2002