Maths-
General
Easy
Question
The diameter of a circular park is 94.4 m. A 2.8 m wide road is constructed outside this circular park, i.e., around it. Find the cost of paving this road at the rate of Rs. 50 square meter
Hint:
Try to find area of the road
The correct answer is: Rs. 42768
Since the road of width 2.8 m is on outside , it means
Diameter of inner circle = 94.4 m
Radius = = = 47.2 m
We know that area of a circle = p r2
Radius of outer circle = Radius of inner circle + Width of road
= 47.2 + 2.8 = 50 m
Area of the road = Area of outer circle – Area of inner circle
= × (50)2 - × (47.2)2
= × ( 50 – 47.2)(50 + 47.2)
( a2 – b2) = (a – b)(a + b)
= 2.8 × 97.2
= 855.36 m2
Now, Cost of constructing 1 m2 road = Rs. 5
Cost of constructing 855.36 m2 road = Rs. 50 855.36
= Rs. 42768
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