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  Number and Math Play

Clockwork
 
Q Three clocks in the train station give the following readings:

CLOCK A:   8:00 CLOCK B:   8:50 CLOCK C:   8:20

One clock is 20 minutes fast. One clock is slow. One clock is off by half an hour.

Help the passengers figure out what time it really is.
 

 
A The time is 8:30. To get the answer, make a chart listing all the possibilities:

20 MIN. FAST SLOW OFF BY 1/2 HOUR
8:00 (real time 7:40) 8:50 (no good--would be fast) 8:20 (no good--real time would have to be 7:50 or 8:50)
8:00 (real time is 7:40) 8:20 (no good--would be fast) 8:50 (no good--real time would have to be 8:20 or 9:20)
8:50 (real time is 8:30) 8:00 (ok-would be slow) 8:20 (no good--real time would have to be 7:50 or 8:50)
8:50 (real time is 8:30) 8:20 (ok-would be slow) 8:00 (ok--real time would have to be 7:30 or 8:30)
8:20 (real time is 8:00) 8:00 (ok-would be slow) 8:50 (no good--real time would have to be 8:20 or 9:20)
8:20 (real time is 8:00) 8:50 (no good-would be fast) 8:00 (no good--real time would have to be 7:30 or 8:30)

The fourth row in the chart is the only one in which all the information given in the puzzle can be true.