Integrated knowledge of rational number notations predicts children’s math achievement and understanding of numerical magnitudes

We propose that integrated number sense, the ability to fluidly translate and compare magnitudes within and across notations, is central to understanding of rational numbers. Consistent with this hypothesis, two studies of 6th through 8th grade students (N = 264 and N = 46) indicated that accuracy comparing magnitudes within and across notations predicted overall math achievement and fraction number line and arithmetic estimation accuracy. Cross-notation magnitude comparison accuracy (i.e., fraction vs. decimal, percentage vs. fraction, and percentage vs. decimal) accounted for variance in math outcomes beyond that explained by magnitude representations within individual notations. The findings also revealed a percentages-are-larger bias, in which percentages are perceived as larger than equivalent fractions and decimals in cross-notation comparisons. There were no differences by grade level, suggesting that such number sense does not necessarily develop with age. Explicitly promoting integrated number sense may help improve mathematics instruction.