# Farsley Farfield Class 6S blog

## Jessica makes a marvellous mistake while deciphering Roman numerals

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Look at these two pictures. One is correct while the other one is not. Can you figure out which one Jess made a mistake on? Jess spotted her own error when she referred back to her rules for deciphering Roman numerals

When deciphering Roman numerals, a key rule is:

If the numeral to the left of another numeral is worth less, you subtract its value from the one on the right.

eg IX = 10 – 1 = 9

With longer numbers you must read each sequence of numerals carefully. In this way you can find the pairs of numerals which may need to go through some ‘subtractive notation’.

eg MCMLXXIV

M (1000)   CM (1000 – 100 =900)  LXX (50 + 10 + 10 = 70) IV  (5 – 1 = 4)

The answer is 1974 – the year tha this blogger was born!

Well done Jess for making this marvellous mistake and showing us all the importance of finding pairs of numerals that require a little subtraction to get the correct answer.