In the given figure, if $AB = AC$, then prove that $BE = EC$. 
Step 1: Given.
A circle is inscribed in $\triangle ABC$ touching sides $BC, CA, AB$ at $E, F, D$ respectively, and $AB = AC$.
Step 2: Use tangent properties.
Tangents drawn from an external point to a circle are equal in length. Thus,

Step 3: Since $AB = AC$.
\[ AD + BD = AF + CF \] Substitute $AD = AF$: \[ BD = CF \]
Step 4: Add equal parts.
\[ BD + BE = CF + CE \Rightarrow BE = CE \]
Step 5: Conclusion.
Hence, in $\triangle ABC$ where $AB = AC$, we have $\boxed{BE = EC}$.
In the adjoining figure, $\triangle CAB$ is a right triangle, right angled at A and $AD \perp BC$. Prove that $\triangle ADB \sim \triangle CDA$. Further, if $BC = 10$ cm and $CD = 2$ cm, find the length of AD. 
In the diagram, the lines QR and ST are parallel to each other. The shortest distance between these two lines is half the shortest distance between the point P and the line QR. What is the ratio of the area of the triangle PST to the area of the trapezium SQRT?
Note: The figure shown is representative

\( AB \) is a diameter of the circle. Compare:
Quantity A: The length of \( AB \)
Quantity B: The average (arithmetic mean) of the lengths of \( AC \) and \( AD \). 
O is the center of the circle above. 
Find the unknown frequency if 24 is the median of the following frequency distribution:
\[\begin{array}{|c|c|c|c|c|c|} \hline \text{Class-interval} & 0-10 & 10-20 & 20-30 & 30-40 & 40-50 \\ \hline \text{Frequency} & 5 & 25 & 25 & \text{$p$} & 7 \\ \hline \end{array}\]