Students encounter difficulties in solving areas of triangles and quadrilaterals due to a lack of conceptual understanding of the topic. The researchers have developed the following activities and the hypothetical learning trajectory (HLT) through the design research approach focusing on developing activities for students to learn the concepts properly. Reallotment or reshaping has been the primary idea for the activities. The designed activities in 2 cycles have been trialled out, improved, and implemented for 7-grade students in a classroom. Students' understanding and development of this study will be further discussed in this paper.