Question 365565
Hello, 
Let's go through this. (The book is correct)
v=1/3(pi)h^2(3r-h) 
First divide both sides by 1/3(pi)h^2 to get:
v/[1/3(pi)h^2]=(3r-h)
Add h to both sides:
v/[1/3(pi)h^2]+h=3r
Note: the 1/3 could actually be written as:
3v/[(pi)h^2]+h=3r
Now divide each side by 3 to get:
r=3v/3[(pi)h^2]+h/3 
Now, we want to combine these two fractions 3v/3[(pi)h^2] and h/3 into one fraction. 
To do so we need a common denominator.
Multiply the (h/3) by (pi)h^2]/(pi)h^2] to get:
h(pi)h^2/3[(pi)h^2] or rewritten as:
(pi)h^3/3[(pi)h^2]
Now that we have the same denominator it looks like:
r=3v+(pi)h^3/3(pi)h^2
OK, hope you followed me on this. 
Does it make sense to you?
RJ
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