SOLUTION: How long does it take $775 to double if it invested at 5% interest compounded semiannually ?

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Question 956464: How long does it take $775 to double if it invested at 5% interest compounded semiannually ?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+A+=+P%2A%28+1+%2B+r%2Fn+%29%5E%28n%2At%29+
+n+=+2+
+r+=+.05+
+P+=+775+
+A+=+2%2A775+
----------------
+1550+=+775%2A%28++1+%2B+.05%2F2+%29%5E%28+2t+%29+
+2+=+%28+1+%2B+.025+%29%5E%28+2t+%29+
+1.025%5E%282t%29+=+2+
Take the log of both sides
+2t%2Alog%28+1.025+%29+=+log%282%29+
+2t%2A.010724+=+.30103+
+t+=+.30103+%2F+.021448+
+t+=+14.0353+
--------------
In 14 yrs, $775 will double
+2+=+%28+1+%2B+.025+%29%5E%28+2t+%29+
+2+=+1.025%5E%28+2t+%29+
+2+=+1.025%5E%28+2%2A14.0353+%29+
+2+=+1.025%5E28.0706+
+2+=+1.99998+
close enough