But these machines were by no means the first calculators, and [What Will Makes ... mechanical processes behind addition, subtraction, multiplication, and division, showing us such intricacies ...
You can look at multiplication as repeated addition ... If you don't have a calculator, the grid method can really help. First, break down your numbers into hundreds, tens and units.
Dividing by fractions. Dividing by a number is equivalent to multiplying by the reciprocal of that number. But what's a reciprocal? The reciprocal of any fraction is that same fraction ...