If the scale of two maps are (a;1:100,000 and b;1:400,000) what is the ground distance if the distance between two towns on the maps is 10cm

A.

10km, 40km

B.

5km, 20km

C.

2.5km, 10km

D.

20km, 80km

Correct answer is A

map distance = 10cm, ground distance = ?
Map scale for (a) 1:100,000
Ground distance = 10 x 100,000/100,000 =10km
Map scale for (b) 1:400,000
Ground distance = 10 x 400,000/100,000 =40km