A Story of Numbers

How people have written numbers: Roman numerals, Egyptian symbols, Mesopotamian base 60, Mayan base 20, and the Indian place value system with zero.

Key ideas

• Roman numerals add symbols, but a smaller symbol before a larger one is subtracted: IV = 4, XC = 90. There is no zero.
• Egyptian numbers repeat a symbol for each unit of each place: stroke 1, heel bone 10, coil of rope 100, lotus 1000, finger 10 000, tadpole 100 000.
• The Mesopotamians counted in base 60, which survives in 60 seconds and 60 minutes.
• The Maya counted in base 20 using a dot (1), a bar (5) and a shell for zero.
• The Indian system uses ten digits, place value and zero, so every number has a short, unique form.
• Zero as a number, with rules for adding and multiplying it, was set out by Brahmagupta.

Remember

Watch out

• Writing IIII or VV instead of IV or X.
• Putting a smaller symbol before a much larger one: 99 is XCIX, not IC.
• Reading a base-60 or base-20 number as if it were base 10.

Worked example