Two stacks of 23 quarters each are shown below. One stack forms a cylinder but the other stack does not form a cylinder.

Complete question:

Two stacks of 23 quarters each are shown below. One stack forms a cylinder but the other stack does not form a cylinder.

Use Cavelieri’s principle to explain why the volumes of these two stacks of quarters are equal.

In this image, we have 2 stacks, whereby one stack forms a cylinder and the other stack doesn't form a cylinder.

We are required to use Cavelieri’s principle to explain why the volumes of the two stacks of quarters are equal.

Cavelieri’s principle states that the volume of two solid figures will be equal if both figures have equal height, the distance from their respective base is equal and their corresponding cross section are of the same area.

Here, we can see that the quater of each stack have the same base area. Since, both quaters have the same base area, there will be no difference in the area of the cross section of both stacks.  

The volume of these 2 stacks of quarters will be equal because both stacks have have the same height of 23 quaters.

let's add {f(x)=x+1}f(x)=x+1 and {g(x)=2x}g(x)=2x together to make a new function.

f(x)+g(x) =(x+1)+(2x)=x+1+2x=3x+1

let's call this new function hh. so we have:

{h(x)}={f(x)}+{g(x)}{=3x+1}h(x)=f(x)+g(x)=3x+1

we can also evaluate combined functions for particular inputs. let's evaluate function hh above for x=2x=2. below are two ways of doing this.

method 1: substitute x=2x=2 into the combined function hh.

h(x)

h(2)

​    

=3x+1

=3(2)+1

=7

​ since h(x)=f(x)+g(x)h(x)=f(x)+g(x), we can also find h(2)h(2) by finding f(2) +g(2)f(2)+g(2).

first, let's find f(2)f(2):

f(x)

f(2)

​    

=x+1

=2+1

=3

​  

now, let's find g(2)g(2):

g(x)

g(2)

​    

=2x

=2⋅2

=4

​  

so f(2)+g(2)=3+4=\greend7f(2)+g(2)=3+4=7.

notice that substituting x =2x=2 directly into function hh and finding f(2) + g(2)f(2)+g(2) gave us the same answer!