On Slopes of Cancellable Numbers

Abstract

A cancellable number (CN) is a fraction in which a decimal digit can be removed (“‘canceled”) in the numerator and denominator without changing the value of the number; examples include $\frac{64}{16}$ where the 6 can be canceled and $\frac{98}{49}$ where the 9 can be canceled. We show that the slope of the line of a cancellable number need not be negative.