How do you multiply 19 by 19 using roman numerals?

Answer 1

First of all today we write out 19 in Roman numerals as XIX but the Romans themselves would have probably calculated 19 as XVIIII and then simplified it to IXX in fact the Latin word for IXX is 'undeviginti' which literally means one from twenty.

So the question is: What is IXX squared?

IXX squared = -I(-I+XX)+XX(-I+XX)

Multiplying out the brackets = +I-XX-XX+CCCC

Collecting like terms = -XXXX+CCCC+I (401-40)

When simplified = CCCLXI (361) which is the answer to your question.

Note that in maths a minus number multiplied by a minus number becomes a plus number. Thus -I times -I is +I.