The scale on a map is 1 : 500000
Two towns are 7cm apart on the map

1 : 500,000
multiplied by 7 cm is
7 cm : 3,500,000 cm
= 7 cm : 35000.00 m . . . (100 cm in 1 m)
= 7 cm : 35 km . . . (1000 m in 1 km)
The actual distance between the towns is 35 km.