In my 5th grade classroom, we use a math review series that's engaging and entertaining at the same time. In essence they are simply halfpage handouts with ten standards based math problems woven into a special picture or exciting scene. Remember, I want to keep the math review time quick, but effective.
For this reason, attractive, well-illustrated worksheets with something to do will make learning fun for them. What's more, completing your worksheet will give the child a tremendous sense of fulfillment.
There are other sources for worksheets also. You can find many public schools and private schools which will provide free worksheets for you if you buy textbooks from the school.
There are several standard exercises which train students to convert percentages, decimals and fractions. Converting percentage to decimals for example is actually as simple as moving the decimal point two places to the left and losing the percent sign "%." Thus 89% is equal to 0.89. Expressed in fraction, that would be 89/100. When you drill kids to do this often enough, they learn to do conversion almost instinctively.