Struck by the apparent innocent charm of the place, Andrea, Brendan and Carl entered an amusement park. They saw a set of three Ferris wheels, all the same size. Andrea, Brendan and Carl each took a seat on each of the Ferris wheels.
Then their bad luck began. They heard over the P.A. system that the Ferris wheels would not stop until they were lined up again. Andrea's Ferris wheel completes a revolution every 40 seconds. Brendan's Ferris wheel completes a revolution every 2 minutes. Carl's Ferris wheel completes a revolution every 90 seconds.
How long must Andrea, Brendan and Carl ride the ferris wheels?
Submit your solution to Minus@actden.com
Deadline for submissions is June 11, 1996 by 12:00 PM (Pacific Time).