This set of four worksheets will help challenge your students, with problems such as, "Find 25% of 20% of 400?" With the help of a chart that is provided, they may readily convert this problem to, 'find 1/4 of 1/5 of 400?' which they may do using mental math skills. You may want to use two worksheets as practice and two as quizzes - convenient! The answer keys are provided.