When a child learns to relate math to everyday questions, he will be great at it from the simplest addition all the way to trigonometry. To convert percentages, decimals and fractions is thus one essential skill.
Parents, too, can start to see math as the enemy. Teachers may even tell parents that their child "struggles with concepts," a nice way of saying "your kid doesn't get it." But is this the case? Does a middle-school child struggling with math simply not understand the concepts? Often the answer to this question is a resounding "no!"
For example, since I want to make sure my students get accustomed to reviewing the various math concepts and standards we've learned all year, I have them practice regularly. I want them to get to a point where they are so familiar with grade level math content, that solving these types of problems becomes automatic.
However for the most part, when a worksheet is needed to help drill down a procedure, standard, or lesson, its effectiveness can and will vary.