hey there my name is kaylee and today we're going to learn about a different way of
writing and reading numbers from almost 3,000 years ago are you ready let's go
i'm sure you've seen a clock that looks like this but have you ever seen a clock that looks like
this the numbers on this clock are the symbols we're used to seeing these are called arabic
numerals the numbers on this clock are written as symbols that might not look very familiar to you
they're called roman numerals roman numerals were invented by ancient romans in 500 bc as a way to
represent numbers and do basic math like addition and subtraction as the roman empire spread so did
the use of roman numerals until much of europe and north africa was using roman numerals to represent
numbers in this lesson we're going to learn how to read and write roman numerals and some general
rules these symbols follow did you know you can use just these three symbols to count to ten
i is one v is five and x is ten so how do we count every number to ten with only these
let me show you here's how we count from one to three in roman numerals
one two three pretty easy right can you guess what four looks like in roman numerals
if you guessed four ones you're actually not correct the actual roman numeral for the number
four is i v say what seems tricky right so now i will tell you the first rule of roman numerals
we can never use more than three of the same symbols in a row that's why we can't write four
as four i's this fourth identical symbol breaks the rule okay so back to our symbol for four iv
we know that the i represents one but what does this v mean v is the symbol for five nice
so let's take a second to think about our symbol for the number four by putting an i before
v what we really said was five take away one so this is another rule of roman numerals
whenever we put an i before a symbol what we're really saying is one subtracted from that number
before we finish counting to 10 let's review our two rules rule one says we can't put more
than three identical symbols in a row that's why when we're writing four we can't write it as four
i's it's not allowed and rule two says any time we put an i in front of a bigger symbol like v
it means we subtract 1 from the bigger number now let's start where we left off at 5. we know
the symbol for five is v can you guess what the symbol for six is it's just the opposite of four
the symbol for six is v i time for another rule when we have a symbol for a smaller number like i
for one after a larger symbol like v for five that means we add the larger number
so now let's use this rule and what we know about putting identical symbols
next to each other and come up with the roman numerals for seven what do you think
that's right v i i is seven now how about eight we can use those same two rules that tell us
that v i i i is eight now let's make sure we understand this
so b is equal to five and we have the symbols for the smaller numbers after v and that means we
add so this is saying 5 plus 1 plus 1 plus 1 which is 8 perfect but what
do you notice about our symbol for 8 how many identical symbols are there in a row
yeah we have 3 i's in a row so how do i write out nine we can't just add another i to eight
we need to know the symbol for ten x is the roman numeral symbol for ten
so how do those ancient romans write the number nine that's right just like we wrote four
is five minus one we can write nine as ten minus 1 which will look like i x
so now we can add a third rule to our roman numeral rules what rule helped us write 6 7 and 8.
rule 3 says an i after a symbol for a larger number like v means add to the larger number
great work you're ready to read and write using roman numerals i v and x on your own join me in
the next video to learn about reading and writing to 39 in roman numerals you can practice reading
and writing up to 10 on your own in the lesson there will be a few questions towards the end
where you have to add all you need to do is think about what the roman numerals represent add them
together to find the sum that's also written as a roman numeral have fun and remember to always be
clever