Dionne is running clockwise. She can run around a circular track in 120 seconds. Basha, running counter-clockwise, meets Dionne every 48 seconds. Sandra runs clockwise and passes Basha every 240 seconds. How often does Sandra meet Dionne in 10 minutes?

Answer 1

Let Tb be the one-lap time for Basha.
The frequency that Basha and Dionne encounter is
1/48 = 1/120 + 1/Tb, so
1/Tb = 10/480 - 4/480 = 6/480 = 1/80
Tb = 80 seconds
With Sandra and Basha running in opposite directions, and Basha running so fast, they would have to meet more often than every 240 seonds. I believe you made and error stating that Sandra runs clockwise, opposeite to Basha. Check the wording of the problem again.