Length of Pendulum Increading by Factor of 9 Increaeses Period By 1 Second - Find Length and Period

If the length of a simple pendulum increases by a factor of 9, the period increases from  
\[t\]
  to  
\[t+1\]
. What is  
\[T\]
  and what is the length of the pendulum?
The period of a pendulum is given by  
\[T= 2 \pi \sqrt{ \frac{l}{g}}\]
.
Originally  
\[t= 2 \pi \sqrt{ \frac{L}{g}}\]
, and then  
\[t+1= 2 \pi \sqrt{ \frac{9L}{g}}\]
.
Dividing the second equation by the first gives  
\[\frac{t+1}{t}= \sqrt{9}=3\]
.
Then  
\[t+1=3t \rightarrow 1=2t \rightarrow t=0.5\]
.
Then  
\[T= 2 \pi \sqrt{\frac{l}{g}} \rightarrow l = \frac{gT^2}{4 \pi^2} =\frac{9.8 \times 0.5^2}{39.47}=0.062\]
m to 3 decimal places.

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