Answer:
increased by 9 times
Explanation:
As the period of a simple pendulum is defined as the following formula
[tex]T = 2\pi\sqrt{\frac{L}{g}}[/tex]
where L is the length of the pendulum and g is the constant gravitational acceleration. Since L is under a square root, if you want to triple the period of vibration, L must be increased by 9 times so that [tex]\sqrt{9} = 3[/tex]
