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?

The spider walks anticlockwise for 5 min and covers a 25 minutes span on the clock.  It meets the minute hand (at the 5 minute position) and turns around.  5 minutes later the minute hand reads 10 minutes after and the spider has walked to the 30 minute mark (5  plus 25).  Another 5 minutes later, the clock minute hand reads 15 minutes after and the spider is now at 55 minutes after 6 (30 plus 25).  In another 5 minutes, the clock reads 20 minutes after and the spider has walked another 25 minute span from the 55 minute to the 20 minute after. He meets the minute hand for the second time!!

 

 

Posted by Mike on 2006-05-15 22:26:01