The airport is 2,000' above the 1003 hPa QNH Pressure Datum.

 

This is 10 hPa above the 1013 hPa Pressure Level, which places the QNH Datum 10 hPa x 30' = 300' above the 1013 Pressure Level.

 

Therefore, the airport is 2,000' + 300' = 2,300' above the Pressure Level, i.e. FL 023.

 

The aircraft climbs from FL 023 to FL 050 = 2,700'.

 

At a rate of 500' fpm, this equals 2,700 / 500 = 5.4 minutes (0.09 hours)

 

Groundspeed = 100 KTAS - 20 kts Headwind = 80 kts

 

 

On CRP 5:

 

Place 1:60 Index on Inner Scale against 80 kts GS on Outer Scale

 

Read 5.4 minutes on Inner Scale against 7.2 NM on Outer Scale

 

 

Mathematically:

 

Distance = Speed x Time

 

Distance = 80 kts  x 0.09 hours

 

Distance = 7.2 NM