Revolved triangle
The area of a triangle with sides 7, 8 and 9 is revolved about the side 9. If the volume of the resulting solid can be expressed in the form M × π , find 3 M .
The answer is 320.
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2 solutions
A
r
e
a
=
4
2
4
∗
1
0
∗
8
∗
6
=
1
2
5
.
A
l
t
i
t
u
d
e
o
n
s
i
d
e
9
,
h
9
=
9
2
∗
a
r
e
a
=
9
2
∗
1
2
5
.
∴
c
g
a
t
a
⊥
d
i
s
t
a
n
c
e
o
f
3
h
9
.
V
o
l
u
m
e
=
2
∗
π
∗
3
h
9
∗
a
r
e
a
=
3
2
0
∗
π
.
S
o
M
=
3
2
0
.
P
a
p
p
u
s
T
h
e
o
r
e
m
.
V
o
l
u
m
e
o
f
r
e
v
o
l
u
t
i
o
n
=
p
a
t
h
t
r
a
c
e
d
b
y
c
g
∗
m
a
s
s
/
a
r
e
a
.
I missed it because of pressing the box without filling the answer !!
This is easy though.. :3
Not very easy though.. Nice problem.. ;-)