Select all the pairs of ratios that form a proportion.
A. 1:6, 4:20
B. 7:9, 28:36
C. 14:18, 21:27
D. 30:80, 6:18
A. 1:6, 4:20 form a proportion because if we simplify 4:20, we get 1:5 which is the same as 1:6.
B. 7:9, 28:36 form a proportion because if we simplify 28:36, we get 7:9.
C. 14:18, 21:27 form a proportion because if we simplify 14:18, we get 7:9 and if we simplify 21:27, we also get 7:9.
D. 30:80, 6:18 do not form a proportion because if we simplify 30:80, we get 3:8 which is not equivalent to 6:18.