A bus stop is barricaded from the remaining part of the road by using 50 hollow cones made of recycled cardboard. Each one has a base diameter of 40cm and height 1m. If the outer side of each of the cones is to be painted and the cost of painting is ₹ 25 per m2, what will be the cost of painting all these cones? (Use π = 3.14 and √1.04 = 1.02.)
ANSWER:
It is given that
Radius of the cone = 20cm = 0.2m
Height of the cone = 1m
We know that
Slant height l = √ (r2 + h2)
By substituting the values
l = √ (0.22 + 12)
On further calculation
l = √ (0.04 + 1) = √ 1.04
So we get
l = 1.02m
We know that
The curved surface area of cone = πrl
By substituting the values
Curved surface area of cone = 3.14 × 0.2 × 1.02
On further calculation
The curved surface area of cone = 0.64056 m2
So, the curved surface area of 50 cones = 50 × 0.64056 = 32.028 m2
It is given that
The cost of painting = ₹ 25 per m2
So the cost of painting 32.028 m2 area = ₹ 25 × 32.028 = ₹ 800.70
Therefore, the cost of painting all of these cones is ₹ 800.70.
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