how can opening a closed problem help?

URN:NBN:SI:DOC-Y7KKJGGU2014Ambrus, Andrásdocuments/doc/Y/URN_NBN_SI_doc-Y7KKJGGU_001.pdfdocuments/doc/Y/URN_NBN_SI_doc-Y7KKJGGU_001.txt24articlestr. 105-120101061851855-9719URN:NBN:SI:doc-Y7KKJGGUengPedagoška fakulteta Univerze v LjubljaniCEPS journalInClearningmatematikamathematicsmožganiproblem solvingreševanje problemovučenjeučne metodehow can opening a closed problem help?Teaching mathematical problem-solving with the brain in mind