If that worked it was only by chance. There was no scale given other than the meridian. The explanation was:
(Refer to Diagram)
From the North Pole on the diagram the aircraft flies down the 110°East meridian.
The meridians are shown every 10° of longitude.
The distance travelled is 480 NM which is equal to 8° of latitude.
Use the latitude scale to measure the distance flown from the pole down the 110° East meridian.
The aircraft is now at 82°N 110°E.
At this point draw in grid North parallel to the Greenwich meridian and plot a track of 154° Grid from 82°N 110°E.
The aircraft travels 300 NM along this track which is equal to 5° of latitude.
Use the latitude scale to measure this 300 NM, plot it onto the chart and you should find the aircraft will be at or close to 80°N 080°E.