A wall clock takes 10 seconds to strike 6. How much time it will take to strike 12.

Explanation

Between 1 o.clock to 6 o.clock there are 5 gaps of time.

Now 5 intervals of time takes 10 seconds so 1 interval of time takes 2 seconds, i.e. we hear the strike in a clock after every 2 seconds. Now 12 strikes will have 11 intervals which takes 11 `xx` 2 i.e. 22 seconds.