The original flock gains 30-20=<<30-20=10>>10 ducks per year

So after 5 years they have gained 10*5=<<10*5=50>>50 ducks

So the original flock has 100+50=<<100+50=150>>150 ducks

So the combined flock has 150+150=<<150+150=300>>300 ducks

# Answer

300
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Every year 20 ducks from a flock are killed but another 30 are born.  The original flock size is 100 ducks.  After 5 years they join with another flock of 150 ducks.  How many ducks are in the combined flock?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
300
Every year 20 ducks from a flock are killed but another 30 are born.  The original flock size is 100 ducks.  After 5 years they join with another flock of 150 ducks.  How many ducks are in the combined flock?
train