At exactly six o'clock, a spider started to walk at a constant speed from the hour hand anticlockwise round the edge of the clock face. When it reached the minute hand, it turned round (assume the turn was instantaneous) and walked in the opposite direction at the same constant speed. It reached the minute hand again after 20 minutes. At what time was this second meeting?

In 1 min., the minute needle travells 30/5=6 degrees.

In 20 minutes, the minute needle would have travelled 120 degrees.

In the same time the spider covered 360+120=480 degrees.

So, it's speed is 480/20=24 degrees per min..

So, the first time they met must have been after 180/(24+6)=180/30=6mins..

So, the second time they met must have been at 6:26. 

Posted by Sparsh on 2006-05-11 12:36:21