A petrol tank is in the form of a frustum of a cone of height 20 m with diameters of it's lower and upper ends as 20m and 50 m respectively . Find the cost of petrol which can fill the tank completely at the rate of RS. 70 per litre . Also find the surface area of the tank
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Answer:
Total cost = Rs 14,28,700
Surface area of frustum = 2750 m² .
Step-by-step explanation:
Given :
Upper diameter = 50 m
= > Radius ( R ) = 25 m
Lower diameter = 20 m
= > Radius ( r ) = 10 m
Height ( h ) = 20 m
Now we know :
Volume of frustum of a cone = π h / 3 ( R² + r² + R r )
Putting value here :
= > π × 20 / 3 ( 25² + 10² + 250 ) m³
= > 6500 π m³
Now convert it into litres.
= > 6500 π × 10³ L
Now :
For 1 L = Rs 70
Total cost = Rs 6500 π × 10³ × 70
Total cost = Rs 6500 × 22 / 7 × 10³ × 70
Total cost = Rs 14,28,700
Now :
We know :
Surface area of frustum = π l × ( R + r )
l² = R² + r²
l = 25 m
Surface area of frustum = 22 /7 × 25 ( 25 + 10 ) m²
Surface area of frustum = 2750 m² .
Hence we get answer.
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