Today Puzzle #560
Puzzle No. 560 鈥� Wednesday 4 September
On 2 Sep the 大象传媒 reported that the number of seals in the Thames Estuary has doubled since the Zoological Society of London carried out its first annual survey in 2013. What is the average annual growth rate?
Today’s #PuzzleForToday has been set by Dr Shaun Fitzgerald, Director of The Royal Institution
Click here for the answer
The growth rate has doubled in 6 years and hence we are seeking the solution of (1+x)6=2 where x is the growth rate. This can be determined by noting that 6 x ln(1+x) = ln (2) = 0.693. Therefore ln(1+x)=0.693/6=0.116. So, (1+x)=exp(0.116)=1.122, and so x=12.2%
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