ABSTRACT
This chapter describes two characteristics that convey the uniqueness of Bob's style: his focus on important topics and his open-mindedness. It describes the main findings from the research. Fraction arithmetic is important. Early performance on fraction arithmetic problems strongly predicts later mathematics achievement, even when potential third variables. Fraction arithmetic is not only important for mathematical achievement, it is also omnipresent in sciences like physics and chemistry, as well as in the workplace. Fraction arithmetic is different from whole-number arithmetic. It calls for different procedures. It also produces different directions of effect. When multiplying whole numbers, the product is always larger than either number in the problem, but when multiplying fractions between zero and one, the product is always smaller than either fraction. Decimals are arguably better suited to communicate the magnitude of rational numbers.
