A tangent $PQ$at a point P of a circle of radius $6 \text{cm}$ meets a line through the centre O at a point Q, so that $OQ=14 \text{cm}$. Length of PQ is :

Make an educated guess based on the conditions stated in the question.

Find the length of PQ using Pythagoras' theorem. 

Radius $\text{OP}=6 \text{cm}$ and $\text{OQ}=14 \text{cm}$

PQ is the tangent to the circle.

$\angle OPQ=90°$

So,by Pythagoras theorem we get,

$P{Q}^2=O{Q}^2-O{P}^2$

$\Rightarrow P{Q}^2={14}^2-6^2$

$\Rightarrow P{Q}^2=196-36$

$\Rightarrow P{Q}^2=160$