Answer:
The answer is 1 : 3 : 2
Explanation:
First, you have to make them into same unit by converting it into km or m :
1 km = 1000 m
0.007 km = 7 m
0.021 km = 21 m
7 : 21 : 14
OR
14 m = 0.014 km
Then you can simplify it by 7 :
m,
7 : 21 : 14
= 1 : 3 : 2
OR
km,
0.007 : 0.021 : 0.014
= 0.001 : 0.003 : 0.002
= 1 : 3 : 2
(take note: in ratio, it is better to put it in whole number form rather than decimal form)