Studies carried out in Latin America (SERCE 2006, and TERCE 2013) demonstrated the low level of dominance in students of subjects such as mathematics in the Panamanian primary education. With this background the present study focused on learning contents related to fundamental arithmetic operations with natural numbers in sixth grade students of Tomas Herrera and Hipolito Perez Tello elementary schools in Chitre. This research was exploratory type to analyze the difficulties presented by the students, and found that missed achievements in the necessary domain, although the official curriculum prescribes that these learnings to be acquired in the first years of the primary education. To test the working hypothesis, the Z Normal test was used. Using this test, the rejection of the null hypothesis was obtained, by accepting the alternative and which ensures that the grades of students is less than 3,0, at a level of significance of 5%.