The wall clock takes $6$ seconds to strike $4$, how much time it will take to strike $12$?

When the clock strikes $4$, there are actually $3$ intervals between strikes: first between strikes $1$ and $2$, second between strikes $2$ and $3$ and third between strikes $3$ and $4$.

So assuming striking itself takes no time, time of each interval $=\frac{6}{3}=2$ seconds.

When striking $12$ times, number of intervals $=12-1=11$.

Hence time taken $=11\times 2=22$ seconds