Hours, minutes and the calendar · Usually met around P2
Clock faces with Roman numerals
I on the left takes away; on the right adds.
How to do it
Method
I on the left takes away; on the right adds
IX = 10 − 1 = 9; XI = 10 + 1 = 11
Another way
Read the position
IX sits on the left, where 9 is
In full
Some clock faces use Roman numerals: I is 1, V is 5, X is 10. A smaller numeral to the right of a bigger one adds: VI is 5 + 1 = 6, XII is 10 + 1 + 1 = 12. An I to the left of a bigger one takes away: IV is 5 − 1 = 4, IX is 10 − 1 = 9. So IV and VI, IX and XI must not be mixed up. Telling the time works as on any clock: XII at the top, III on the right, VI at the bottom, IX on the left; the hour hand's last numeral is the hour, and each big step of the minute hand is 5 minutes. Or don't read the numerals at all, just where the hands point: every place is where it is on an ordinary clock.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
This clock face uses Roman numerals. What o'clock does it show?
Show the answer and working
Answer: 11 o'clock
The minute hand points to XII at the top, so it is on the hour; the hour hand points to the numeral for 11: 11 o'clock.
Example 2
This Roman-numeral clock shows □ h □ min.
Fill in each box
Show the answer and working
Answer: 1，15
The hour hand has just passed the numeral for 1; counting the minute hand in fives from XII gives 15 minutes.
Example 3
The Roman numerals on the card make a number bigger than 2.
True or false?
Show the answer and working
Answer: True
Read the numerals first, 11, then compare with 2. Don't go by how many letters: IX has two but is more than VIII.
Practise it in the game →Hours, minutes and the calendar · Free to start, unlimited questions, no download