How many silver coins ,2cm in diameter and of thickness 2mm,must be melted to form a showpiece in the form of frustum of a cone having height 9cm and radii of outer circular ends as5cm 3cm

Answer 1

I assume you can find the volume of a cylindrical coin.

For the frustrum, consider it as a large cone with a small cone cut off the top. If you draw a side view, then if the height of the small top cone is h, you have

(h+9)/5 = h/3
h = 27/2

Now you see that the volume of the frustrum is

π/3 (5^2*(9+27/2) - 3^2*27/2) = 147π

Now just divide the volume of the frustrum by that of the coin to get the number of coins.

Answer 2

Right answer and good solutions