If Mark bought 50 cans of milk, the number of times Jennifer added 6 cans for every 5 that Mark bought is 50/5 = <<50/5=10>>10 times.
The total number of additional cans she bought is 10*6 = <<10*6=60>>60 cans.
If she initially had 40 cans, she went home with 40+60 = <<40+60=100>>100 cans of milk.
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