How_To_Be_Good_At_Math

NUMBERS • NUMBER SYMBOLS 11

Reading long numbers and dates

To turn a long Roman number or date into a Hindu-Arabic

number, we break it into smaller parts then add up the parts.

MCMXCVIII

IV V VI VII VIII IX

Answers on page 319

TRY IT OUT

The Babylonian number system is

more than 5000 years old

REAL WORLD MATHS

4 5 6 7 8 9

Now have a try at writing these

years as Roman numerals:

1666 2015

“C” before “M” means

“100 less than 1000”

Let’s work out the

number CMLXXXII.

First, we break it into

four sections.

Next, we work out

the values of the

different sections. When

we add the values

together, we get the

answer: 982.

= 900 +

= 50

= 30

= 2

982

1000 − 100

L

3 × 10

2 × 1

What’s this year?

Zeros help us

read the time

correctly on a

24-hour clock

=

=

=

Zero the hero

Not all number systems have a symbol for zero

(0) as we do. On its own, zero stands for “nothing”,

but when it’s part of a bigger number, it’s called the

place holder. This means it “holds the place” when

there is no other digit in that position of a number.

The Romans used letters as

symbols for numbers

CM L XXX II

CM

XXX

II

Name the date

Today, we sometimes see dates written

in Roman numerals. Can you use what

you’ve learned to work out these years?

09:

010_011_Number_symbols.indd 11 29/02/2016 14: