Roman numerals · Usually met around P3
Roman numerals to 100
Split into tens and ones, then write each.
How to do it
Method
Split into tens and ones, then write each
47 = XL + VII = XLVII
Another way
Left to right
XCIV = 90 + 4 = 94
In full
Two more letters: L is 50 and C is 100. Write the tens and the ones separately: the tens use X, L and C just as the ones use I, V and X, so 40 is XL (50 − 10) and 90 is XC (100 − 10), as 4 is IV and 9 is IX. To write a number, split it into tens and ones first: 47 = 40 + 7 = XL + VII = XLVII. To read one, you can also go left to right, taking away a smaller letter that comes before a bigger one: XLVII = 50 − 10 + 5 + 1 + 1 = 47. Only four pairs take away: IV, IX, XL and XC.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
Which pair of letters writes 4?
- A. IV
- B. IX
- C. XL
- D. XC
Choose the right answer
Show the answer and working
Answer: A. IV
A smaller letter before a bigger one takes away: IV = 5 − 1, IX = 10 − 1, XL = 50 − 10, XC = 100 − 10. 4 is one of these.
Example 2
The numerals on the tablets go up by the same amount each time. What number does “?” stand for?
Show the answer and working
Answer: 85
The first is 55 and each one is 10 more: “?” is tablet 4, so it stands for 85.
Example 3
Make one Roman numeral from the letter cards in the picture, using every card exactly once. What is the biggest number you can make?
Show the answer and working
Answer: 55
For the biggest, take nothing away: put the 2 cards from biggest to smallest and add them all: 55.
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