One adult and 10 children are in an elevator. If the adult's weight is 4 times the average (arithmetic mean) weight of the children, then the adult's weight is what fraction of the total weight of the 11 people in the elevator?

Ok so this means that the Adult weighs 4 times as much as the kids do because there is only one adult what we can do is add 4 to the total amount of kids in the elevator and subtract 1 from the adult amount, so now we have 14 kids in the elevator (however 4 of them are a adult) so that means that 4/14 is ratio of weight from adults to kids is and 4/14 can be reduced down to 2/7 Enjoy!=)