The chart's scale illustrates the relationship between the depicted length on the chart and the actual distance on Earth's surface and is commonly expressed as a fraction, for example"1: 250 000":

• Chart Scale = Chart distance (CD) / Earth distance (ED)

The scale is dimensionless, because both numerator (CD) and denominator (ED) have the same units of measurment.

In this scenario, as the units of length in the options are in different formats, we need to convert them to a common unit:

• 1 NM = 1 852 m
• So, 220 NM = (220x1 852) 407 440 m x 100 cm = 40 744 000 cm

So, with the given information:

• 1/Scale = 40.7 cm / 40 744 000 cm = 1/1 000 000 or 1: 1 000 000 approximately.