If there are 7 books on the floor, 7 x 3 is 21. Plus two extra books, 21 + 2 = 23. There are 23 books on the bookshelf.
 
        
             
        
        
        
Answer:
2
Step-by-step explanation:
 
        
             
        
        
        
Answer:
I believe its B, But I am unsure since I haven't done geometry in a couple years.
 
        
             
        
        
        
Yay, I like das stuff
I think I learned the washer method
goes like this

ok, so 
actuallly, this is easier
y=49-x^2 and
y=0
see when they intersect again
they intersect at -7 and 7
if we do integrate from -7 to 7, then it wil give 0 (because integration is area under the curve), so note that they are same both sides so integrate from 0 to 7 then double the volume to get both sides
so it can't be C or D
It also can'nt be A because it should not be multipied by 4, it should be multipied by 2
basically, we don't need the washer method
remember, area=pir^2
the disk method then
we are summing up all the radii disks and squareing them
but doubleing them so 

no idea why we need the inside part to be x(49-x^2), that is intersting
 
        
        
        
<span>100 = 5 * (5+5+5+5)
</span><span>100 = (5*5*5) - (5*5)
</span><span>100 = (55/.5) - (5+5)</span>