Calculations
Upon completing the first piece, ...(Multiplication), I realized I could check its answer by performing the reverse calculation, i.e. division. Specifically, if ...(Multiplication)’s answer was correct, dividing it by one of the initial two numbers would result in the other number. So I constructed the second piece, ...(Division), using the long division method, also taught to me in elementary school. With this method, you calculate the answer one digit at a time, with intermediate steps of subtraction and remainders, writing these below one another and shifting one place to the right each step. After completing a significant amount of the calculation, the answer I was constructing suddenly diverged from ...(Multiplication). After checking my work and ruling out any error in ...(Division), I had to admit that ...(Multiplication) had an error. I decided to work back into the first piece, changing its answer, which in turn, changed the second piece being constructed. Continuing on, I discovered more errors, and it quickly became apparent that ...(Division) and ...(Multiplication) were inextricably linked, one guiding the other to completion. The only assurance on the accuracy of both answers was if ...(Division) ended with its final subtraction having no remainder, i.e. zero, which it thankfully did.