Fragmentation of thinking structures is a phenomenon of constructing information in the brain that is inefficient, thus inhibiting the process of solving mathematical problems. Fragmentation of thought structures can be traced through erroneous constructs in solving mathematical problems. To overcome fragmentation, students need to defragment the thinking structures. Defragmentation is the thinking structure rearrangement through the process of checking, repairing, and ascertaining (CRA) in

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... ing mathematical problems. Students defragment the thinking structure under the researcher assistance through the provision of "limited intervention". Limited interventions are conducted by facilitating the occurrence of disequilibrium, cognitive conflicts, and scaffolding. In this study, five types of defragmentation of thinking structures are described: (1) defragmentation scheme knitting to arrange the occurrence fragmentation of meaningless connections, (2) defragmentation of scheme activation to arrange the occurrence fragmentation of false-pseudo construction, (3) defragmentation of connections emertionto arrange the occurrence fragmentation of nothing connection, (4) defragmentation of scheme translation adjustmentto arrange the occurrence fragmentation of translation of thinking structure, and (5) defragmentation of schemeemertion to arrange the occurrence of fragmentation of construction holes. In this study, students were asked to complete the work sheet and spoke out what was being thought (thinkaloud). In addition, students were also interviewed to explore the data that had been collected. The research data used was the result of think aloud (in the form of written data, verbal, and expression) and interview result.