The purpose of this research was to determine whether or not students in high school chemistry have the prerequisite math skills, the application of equivalent fractions to unit conversions, needed to work dimensional analysis problems in chemistry. If students do not have the math skills but are actively taught them, then they should be able to use this skill to solve chemistry problems. The participants of the study included 78 honors and non-honors high school chemistry students. The math data was analyzed from the fall Northwest Evaluation Association, NWEA, data and correlated with a student's chemistry pretest data involving dimensional analysis. In teaching dimensional analysis, teacher-centered instruction was compared to manipulative-assisted instruction. The teacher-centered instruction involved the use of notes, lecture, and problem worksheets. The manipulative-assisted instruction dealt with the use of unit conversion manipulatives, specifically animal/insect picture cards. Students who used the picture cards were found to have higher average retention test scores compared to those who used the teacher -centered strategy. Although the average score was higher with the picture cards, the increases were not statistically significant. In order to show statistical significance, the cards need to be used earlier in the year or possibly in previous courses for extensive exposure. As students work with the cards, they will internalize dimensional analysis and should improve the retention test scores. Keywords: chemistry, dimensional analysis, mathematics, and unit conversion