The ratio of 50m and 4km is:

(A) 1:20
(B) 1:25
(C) 1:40
(D) 1:80

The answer is: (D) 1:80
Solution
The ratio of 50m and 4km is: 50m/4km = 50m/4000m (1 kilometer = 1000 meters)
Hence, ratio = 50/4000 = 1/80 = 1:80