Please help! It is a mixed proportion question! Can.I see how you got the answer!!?

The time of the full swing of the pendulum caries directly as the square root of it's length. If the time taken is 2.4 seconds when it's length is 144cm find... 1) the time taken when it's length is 100cm. 2) the length when the time taken is 1.8 seconds, Can you please show me how you got the answer aswell, as I have no idea how to work it out!