Twelve flags stand equidistant along the track at the stadium. The runners start at the first flag. A runner reaches the eighth flag 8 seconds after he starts. If he runs at an even speed, how many seconds does he need altogether to reach the twelfth flag?
Answer
He will need 124⁄7 seconds, not 12 seconds.
There are 7 segments from the first flag to the eighth, and 11 from the first to the twelfth. He runs each segment in 8⁄7 seconds; therefore, 11 segments take 88⁄7 = 124⁄7 seconds.