The inner and outer radius of a circular track are, respectively, 29 m and 23 m. The cost of levelling the track at Rs.7/m2 is:
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e Rs.6,864
The area of the circular track in the area of the bigger circle minus the area of the smaller circle.
⇒ Area of track = π(R2 - r2)
⇒ Area of track = π(292 - 232) = π(52 × 6)
⇒ 312πm2
The cost of leveling = the cost of leveling per meter square × total area
⇒ 7 × 312π
⇒ 7 × 312 × (22/7)
⇒ Rs. 6864