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? Let's think step by step and output the final answer after "####".
user
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
#### 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