The goal is to increase the length of the fish by (1%)*(pellets) -correct me if i am wrong.
For instance you have a really big fish,that in a meal ate 200 pellets.Before meal fish's length was 10 m.Now it ate 200 pellets,so it has to grow up.How much?It's previous length plus the length it gained while eating.
length = (pellets) *(1/100);
is translated into this --> New length of the fish = the length it gained while eating.
Why is this false?Because you take into no consider the length that the fish had before the meal.So give it another shot
As for the newbie,no problem