Lessons · Pharmacy · roman numerals on a script
Roman numerals on a script
Prescribers still write quantities in roman numerals, and five letters cover almost all of them: i is 1, v is 5, x is 10, l is 50 and c is 100.
Hone is a place to practise a career, one idea a day. This is one of its lessons, written out in full and free to read without an account.
What it is for
A script that reads Disp: xxx is thirty tablets, and a technician who guesses at it either sends a patient home short or hands over three times what was written. It is a reading skill, not a maths skill, and it takes ten minutes to learn for good.
How to think about it
Read left to right and add, except when a smaller letter sits in front of a bigger one, and then that smaller one is taken away. Write the figures underneath the letters before you add anything.
Worked example
i = 1, v = 5, x = 10The three that cover most scripts.
xxx = 30Three tens, added.
xii = 12Ten, then one, then one.
ix = 9The small one in front takes away: ten less one.
l = 50, c = 100The larger quantities. Disp: c is one hundred.
Your turn
A script says Disp: xl. Write the quantity in figures.
xl =
Solve one, graded on the server
The trap
Reading xl as sixty. The smaller letter in front subtracts, so xl is 40 and lx is 60. One of those scripts is forty tablets and the other is sixty, and they are one letter apart.