‘Counting up’ strategy as an alternative to solve subtraction problems with regrouping

Abstract

This paper intends to explore how the ‘counting up’ strategy on an empty number line could help children overcome their mistakes in performing column subtraction problems that require regrouping. Solving subtraction problems with regrouping in column strategy is often frustrating for most children because it involves regrouping numbers in place value. In this qualitative case study, how two second graders develop their thinking while engaging in a designed instructional activity were observed and analyzed. The data collection included observations, conversational interviews, and children’s written works. The results showed that the designed activity with a measurement context and an empty number line model is found to be helpful for children to develop the idea of ‘counting up’ in solving subtraction problems that require regrouping. The children gradually develop their counting up strategy from jumps of ones to jumps of tens to simplify the use of the empty number line model. The results help us understand that we must provide a meaningful support for children to explore various calculation strategies to improve their flexibility in solving subtraction problems.