Class 10 maths standard 30/4)3 question pls soove it

Solution:
As it is given h is the perpendicular depth of the lid so it makes $CD\perp AB$
As OC is also a straight line thus $CD\perp AB$.
The perpendicular line from the centre of the circle bisects the chord.
Here, AB is a chord and OC is perpendicular to AB.
So, D bisects the chord AB.
$$\begin{gathered} \mathrm{Here}, h=CD=2 \\ BD=\frac{AB}{2}=6 \\ In △BDO, we have \\ O{B}^2=B{D}^2+O{D}^2 \\ {r}^2=6^2+{\left(r-2\right)}^2 \\ \Rightarrow r^2-{\left(r-2\right)}^2=36 \\ \Rightarrow 2\left(2r-2\right)=36 \\ \Rightarrow r=10 \mathrm{cm} \end{gathered}$$