xiii, 140p. :ill.The study focused on comparing the efficiency of the Decomposition (conventional method) and Base Complement Addition (non-conventional method) using two randomized groups ofpupils. The comparison was done on measures of speed, accuracy and retention. In all, sixty pupils (thirty from each school) were selected from St. Peter’s and Jesus Cares Preparatory Schools at Dunkwa Offin in the Upper Denkyira East Municipality in the Central Region of Ghana. The researcher used simple random sampling to select primary three pupils for the study. Pretest-posttest design was used in the study. The t-test and median test (all tested at 0.05 level of significant) were the statistical tools used in the study. The Statistical Package for the Social Sciences (SPSS) was used to analyse the measures of speed, accuracy and retention of the pupils of Decomposition and Base Complement Addition groups. The analysis revealed that Base Complement Addition group performed better than their counterparts in the Decomposition group on measures of speed, accuracy and retention. These differences were significant at 0.05 significant levels. It was recommended that students should be encouraged to conduct further research on the topic in different geographical areas, the sample size must be increased and the intervention period must be extended.