The chart indicates the variation was 3°45'W in 1988, and the annual change is decreasing 6'. If you use the chart in 1991 how much variation should you apply?

Correct Answer: Option A — 3°27'W

Calculate the total change: 3 years (1991-1988) at 6' per year equals 18' of decrease. Since the variation was 3°45'W and is decreasing, subtract 18' from 3°45'. The result is 3°27'W. Annual changes are applied to update chart data per standard navigational practices found in Bowditch.