The inner and outer radii of a circular track are 28 m and 25 m, respectively. The cost (in ₹) of levelling the track at ₹28 per m2 is: [ Use π = ]
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Correct answer: B
Explanation
The correct answer is Option 2 i.e. 13,992.
The area of the track is the area of the outer circle minus the area of the inner circle
Outer radius (R) = 28 m
Ine radius (r) = 25 m
The area of a circle = πr2
r = radius
Area of the outer circle = π × R2
⇒ π × 282 = 784π
Area of the inner circle = π × r2
⇒ π × 252 = 625π
Thus,
Area of track = Area of the outer circle - Area of the inner circle
⇒ 784π - 625π
⇒ 159π
The cost of leveling per square meter is ₹28
Total cost = 159π × 28
⇒ 159 × 22/7 × 28
⇒ 159 × 22 × 4
⇒ 159 × 88 = 13992
Thus,
The cost of leveling the track is approximately ₹13,992