He contacted 1-.4=<<1-.4=.6>>.6 of his friends

So he contacted 100*.6=<<100*.6=60>>60 people

So he removes 60/2=<<60/2=30>>30 people

So he has 100-30=<<100-30=70>>70 friends left

# Answer

70
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Mark realizes that a lot of the friends on his friends list are people he doesn't talk to anymore.  He keeps 40% of his friends list and then contacts the rest.  Of those only 50% respond.  He removes everyone who did not respond.  If he had 100 friends how many does he have left after the removal?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
70
Mark realizes that a lot of the friends on his friends list are people he doesn't talk to anymore.  He keeps 40% of his friends list and then contacts the rest.  Of those only 50% respond.  He removes everyone who did not respond.  If he had 100 friends how many does he have left after the removal?
train