You give tours on the Great Lakes and talk about points of interest. A lighthouse typically has 2 beacons that rotate together—but not necessarily facing opposite directions. In that way, it can be a shorter time between the first and second flashes than between the second flash and the third flash (when the first beacon comes around for the second time). One way of identifying which lighthouse you are looking at is to find the ratio of the short time between flashes to the long time between flashes. If the beacons are set 120° apart along the rotation, as shown below, what is this ratio?

Accepted Solution

If the second beacon is 120° after the first, then the first is 360° -120° = 240° after the second. The ratio of the times between beacons is
  120° : 240° = 1 : 2

The appropriate choice is
  E. 1:2