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A distance of 7.5 cm on an aeronautical chart represents a distance of 60.745 NM in reality. What is the chart scale?

  • A

    1 : 500 000

  • B

    1 : 1 000 000

  • C

    1 : 150 000

  • D

    1 : 1 500 000

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, 60.745 NM = (60.745x1 852) 112 500 m x 100 cm = 11 250 000 cm

So, with the given information:

  • 1/Scale = 7.5 cm / 11 250 000 cm = 1/1 500 000 or 1: 1 500 000 approximately.

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This question has appeared on the real examination, you can find the related countries below.

  • Austro Control