The ratio of chickens to ducks is 5:2. After 120 chickens are sold, this is the ratio of chickens to ducks, which is 9:4

The ratio of chickens to ducks is 5:2. After 120 chickens are sold, this is the ratio of chickens to ducks, which is 9:4

5:2=10:4
10:4-9:4=120
120×4=480
Answer: raise 480 ducks