Question 212195
{{{P=k*sqrt(L)}}}, where k is a constant. 
{{{P^2=KL}}}
{{{K=P^2/L}}}
{{{(P1)^2/L1=(P2)^2/L2}}}
{{{4^2/12=(P2)^2/3}}}
{{{(P2)^2=(4^2*3)/12}}}
{{{P2=4*sqrt(3/12)=4*(1/2)=2}}}
The period is 2 seconds.