surface area of two end: PI(4-2)* two ends
surface are of outer : PI*2*3
surface area of inner: PI*1*3
Total area: PI (3+6+2)
check my thinking.
Another question, hehe: By "two ends", you mean the radii of the circles?
The way I looked at was this :
Surface area of outside cylinder = 2pi(2) = 4pi .... 2pi(r)(h)
Surface area of inside of cylinder = 2pi(1) = 2pi
Surface area of top ("washer" shape) = pi(2^2) - pi(1^2) = 3pi
Now the question becomes whether to include the base in the surface area calculation.
Students in the last few days have been using the definition lateral surface area to exclude the base.
So if we include the base the total surface area would be 4pi + 2pi + 6pi = 12pi
if we exclude it then 9pi
Reiny is right on the ends, 3PI for each. I included the base.
Find the surface area of the resulting SOLID.
R = 2, r = 1, h = 3
Outer cylinder = 2R(Pi)h
Outer cylinder = 2(2)Pi(3) = 12Pi
Inner cylinder = 2r(Pi)h
Inner cylinder = 2(1)Pi(3) = 6Pi
Ends = [PiR^2 - Pi(1^2)]2
Ends = [Pi(2^2)-Pi(1^2)]2 = 6Pi
Total surface area = 24Pi
WHERE DID I GO WRONG, IF I DID??
Lateral surface area of cylinder standing on one end = 2(2)Pi(3) = 12Pi
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