Question

A petrol tank is in the form of a frustum of a cone of height 20m with diameters of its lower and upper ends as 20m and 50m 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.​

Answer 1

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.

Answer 2

Answer:

2850

hope its help uh.... ......