Scale = (Chart distance)/(Earth distance) or CD/ED
CD = 9 cm
ED = 5 x 60 x cos37º = 300 x 0.799 = 239.7nm = 444.32km = 44,432,000 cm
Scale = CD/ED = 9/44,432,000 = 1/4,936,910.5 as good as 1/5,000,000