Keith caught 5 x 2 = <<5*2=10>>10 fish.

Therefore, they caught a total of 5 + 10 = <<5+10=15>>15 fish.

# Answer

15
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Keith and Blaine went fishing. Blaine caught 5 fish while Keith caught twice as many as Blaine's. How many fish did they catch together?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
15
Keith and Blaine went fishing. Blaine caught 5 fish while Keith caught twice as many as Blaine's. How many fish did they catch together?
train