Question

A hollow cylindrical pipe is of length 40 cm its internal and external radii are 4cm and 12cm respectively. It is melted and cast into a solid cylinder of length 20 cm. Find the radius of the new cylinder.

Answer 1

Answer:

r = 16sqrt(pi) cm

Step-by-step explanation:

cylinder volume (cv)= length * pi *r^2

Now let's set the equation as follows:

hollowed_cylinder_vol = new_cast_cylinder_vol

40*pi*12^2 - (40*pi*4^2) = 20*pi*r^2

5120pi = 20r^2

r^2 = 256pi

r = 16sqrt(pi) cm