A non scale model of the earth has a diameter of 12 in. Within an outer clay layer, there is a core made of a golf ball diameter of 2 in. What is the volume of the clay? Use 3.14 to approximate pi and round your answer to one decimal place.

Question

anonymous · Answer

The area of a cylinder is A=2πrh+2πr2

Basically, you want to find the Area of the model Earth minus the area of the gold ball.

Remember, in the equation of above, r mean radius, which is half the diameter.

anonymous · Answer

Equation messed up, $$A = 2\pi rh+2\pi r ^{2}$$

anonymous · Answer

Did you figure it out? Or do you need further explanation?

anonymous · Answer

no I didn't

anonymous · Answer

The shape of the earth is a sphere. Since the model is composed of two layers, it means that the golf ball is the core and the clay forms a spherical shell around the golf ball. 
For a sphere of radius r
$$Volume = \frac{4}{3}\pi r^3$$ 
since we have a sheel|dw:1425187118165:dw|
For the inner sphere we use the formula above and then we consider the outer sphere
R = complete radius of the model = 6 inches (12 inches is the diameter so half of it gives R)$$V_2 = \frac{4}{3}\pi R^3$$ 
for the volume of the clay used subtract the volume of the golf ball from the total volume of the model.
$$Volume - of -clay-used = \frac{4}{3}\pi 6^3- \frac{4}{3}\pi 2^3$$

anonymous · Answer

correction # "shell"- above the figure

anonymous · Answer

so the answer is what

anonymous · Answer

Volume of the clay used = 870.826666 cubic inches ~ 871 cubic inches

anonymous · Answer

the answer is 871