If the length of a simple pendulum is increased by $300\%$,then the time period will be increased by ..... $\%$

The mass and diameter of a planet are twice those of Earth. What will be the period of oscillation of a pendulum on this planet if it is a seconds pendulum on Earth?

$A$ bob of mass $m$ suspended by a thread of length $l$ undergoes simple harmonic oscillations with time period $T$. If the bob is immersed in a liquid that has density $1/4$ times that of the bob and the length of the thread is increased by $1/3$ of the original length,then the time period of the simple harmonic oscillations will be :-

The acceleration due to gravity on the surface of the moon is $1.7 \; m s^{-2}$. What is the time period of a simple pendulum on the surface of the moon if its time period (in $s$) on the surface of the earth is $3.5 \; s$? ($g$ on the surface of the earth is $9.8 \; m s^{-2}$)

Two light strings,each of length $\ell$,are fixed at points $A$ and $B$ on a fixed horizontal rod $xy$. $A$ small bob is tied by both strings and is in equilibrium,the strings are making an angle of $45^{\circ}$ with the rod. If the bob is slightly displaced normal to the plane of the strings and released,then the period of the resulting small oscillation will be:

$A$ simple pendulum is executing simple harmonic motion with a time period $T$. If the length of the pendulum is increased by $21\%$,the percentage increase in the time period of the pendulum of increased length is ..... $\%$