The second flight had 20*2=<<20*2=40>>40 steps

The third had 40-10=<<40-10=30>>30 steps

So in total, he climbed 20+40+30=<<20+40+30=90>>90 steps

So he climbed 90*.5=<<90*.5=45>>45 feet

# Answer

45
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
John climbs 3 staircases.  The first staircase has 20 steps.  The next has twice as many steps as the first.  The final staircase has 10 fewer steps than the second one.  Each step is 0.5 feet.  How many feet did he climb?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
45
John climbs 3 staircases.  The first staircase has 20 steps.  The next has twice as many steps as the first.  The final staircase has 10 fewer steps than the second one.  Each step is 0.5 feet.  How many feet did he climb?
train