SOLUTION: what is the area between two concentric circles having diameters 10 and 18 meters respectively?

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Question 927123: what is the area between two concentric circles having diameters 10 and 18 meters respectively?
Found 2 solutions by josmiceli, Edwin McCravy:
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+A%5B1%5D+=+pi%2Ar%5B1%5D%5E2+
+A%5B2%5D+=+pi%2Ar%5B2%5D%5E2+
--------------------
+r%5B1%5D+=+%281%2F2%29%2Ad%5B1%5D+
+r%5B1%5D+=+%281%2F2%29%2A18+
+r%5B1%5D+=+9+
-------------
+r%5B2%5D+=+%281%2F2%29%2Ad%5B2%5D+
+r%5B2%5D+=+%281%2F2%29%2A10+
+r%5B2%5D+=+5+
---------------
+A%5B1%5D+=+pi%2A9%5E2+
+A%5B1%5D+=+81%2Api+
-----------------
+A%5B2%5D+=+pi%2A5%5E2+
+A%5B2%5D+=+25%2Api+
------------------
Area between the circles =
+A%5B1%5D+-+A%5B2%5D+
+81%2Api+-+25%2Api+=+56%2Api+

Answer by Edwin McCravy(20055) About Me  (Show Source):
You can put this solution on YOUR website!

Edwin
+A%5B1%5D+=+pi%2Ar%5B1%5D%5E2+
+A%5B2%5D+=+pi%2Ar%5B2%5D%5E2+
--------------------
+r%5B1%5D+=+%281%2F2%29%2Ad%5B1%5D+
+r%5B1%5D+=+%281%2F2%29%2A18+
+r%5B1%5D+=+9+
-------------
+r%5B2%5D+=+%281%2F2%29%2Ad%5B2%5D+
+r%5B2%5D+=+%281%2F2%29%2A10+
+r%5B2%5D+=+5+
---------------
+A%5B1%5D+=+pi%2A9%5E2+
+A%5B1%5D+=+81%2Api+
-----------------
+A%5B2%5D+=+pi%2A5%5E2+
+A%5B2%5D+=+25%2Api+
------------------
Area between the circles = 
+A%5B1%5D+-+A%5B2%5D+
+81%2Api+-+25%2Api+=+56%2Api+

josmiceli