Popular Interview Problem
I have two rectangular bars. They have property such that when you light the fire from one end , it will take exactly 60 seconds to get completely burn. However they do not burn at consistent speed (i.e it might be possible that 40 percent burn in 55 seconds and next 60 percent can burn in 10 seconds). Problem is : How do you measure 45 seconds ?



1) Light fire on first bar from both the ends and second bar from one end.

2) After 30 seconds(when first bar gets completely burned out) , burn the second bar from second end as well.

3) When second run completely gets burned , you know its 45 seconds.