Question

A petrol tank is in the form of a frustum of a cone of height 20m with the diameter of its lower and upper ends as 20m&50m.Find the cost of petrol which can fill the tank completely at the rate of rs.70per litre.Also find the surface area of the bank

Answer 1

Pic is attached for answer. Plz check with answers

Answer 2

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.