How do you do British pre-decimal math?

Answer 1

All school kids got used to it very quickly. The maths of predecimal currencies was another reason for the conversion to a decimal based currency system.

There were 12 Pennies in a Shilling, and 20 Shilling in a Pound. That is what you need to remember.

Add these two predecimal values -

£3/15/6 - 3 Pounds, 15 Shillings and 6 Pence.

£2/ 7/ 8 - 2 Pounds, 7 Shillings and 8 Pence.

Add the pennies first. 8 Pence + 6 Pence = 14 Pence. 14 Pence = 1 Shilling and 2 Pence. Put down the 2 Pence and carry the 1 Shilling.

£ / / 2

Next, add the Shillings starting with the carried over 1 Shilling from the Pence addition.

1 Shilling + 7 Shillings + 15 Shillings = 23 Shillings. 23 Shillings = 1 Pound and 3 Shillings. Put down the 3 Shillings and carry the 1 Pound.

£ / 3/ 2

Finally, add the Pounds starting with the carried over 1 Pound from the Shillings addition.

1 Pound + 2 Pound + 3 Pound = 6 Pounds.

£6/ 3/ 2 - Total = 6 Pounds, 3 Shillings and 2 Pence.

Easy. This was mental arithmetic for shopkeepers and other business people in predecimal days.