Volume of prisms and cylinders

Answer:
7)V=16257.74
8)V= 226.19
9)V=12.56
10)V=6283.18
11)r=6.631
12)h=69.05
13)V=35328.78
Step-by-step explanation:
Volume of cylinder is given by formula:
V=πr^2h
where r is radius and h is height of cylinder
7)
r=15
h=23
Putting values in formula:
V= π(15)^2(23)
=5175π
=16257.74
8)
diameter=6
r=d/2=3
height =?
Finding height by pythagoras theorem:
h^2= 10^2-6^2
=100-36
=64
h=8
Putting values in formula:
V=π(3)^2(8)
= 72π
= 226.19
9)
r= 2
h=1
Putting values in formula:
V=π(2)^2(1)
=4π
= 12.56
10)
diameter =20
r=d/2=10
h=20
Putting values in formula:
V=π(10)^2(20)
=2000π
=6283.18
Now finding the missing measures:
11)
Given V=210π
h = 15
r=?
Putting values in formula:
210π=π(r)^2(15)
r^2= 210π/15
=14π
r= 6.631
12)
V=197.82
r=3
h=?
Putting values in formula:
197.82=π(3)^2(h)
h= 197.82/9π
= 69.05
13)
r=21
h=25.5
Putting values in formula:
V= π(21)^2(25.5)
=11245.5π
=35328.78 !