A boy leaves home in the morning to go to school. At the moment he leaves the house he looks at the clock in the mirror. The clock has no number indication and for this reason the boy makes a mistake in interpreting the time (mirror-image). Just assuming the clock must be out of order, the boy cycles to school, where he arrives after twenty minutes. At that moment the clock at school shows a time that is two and a half hours later than the time that the boy saw on the clock at home.
At what time did he reach school?

ANSWER: 13:25

Solution: denote the time( observed by the boy) y minutes after 12:00

the actual time then is -y

so

y+150=-y+20
2y=-130
y=-65 minutes afternoon i.e. 10:55 so real time 1s 13:05 the boy arrived to school 20 minutes later
i.e. about 13:25

ady
Edited on February 7, 2004, 11:58 am

Posted by Ady TZIDON on 2004-02-07 11:04:53