When Frank and Mark finished milking, they found that they had 900 pounds of milk that was 2% butterfat. How much butterfat did they have to add to raise the butterfat content to 10%?
The added butterfat weighs
The number of pounds of butterfat in the 900 pounds of milk was
Then we can say that there was 982 lbs of not-butterfat.
Assume we add enough butterfat that the mixture has 10% butterfat. Let the total weight of the final mixture be
As a percentage,
Therefore the added butterfat must weigh
I hope this helps,