To multiply by 12 1/2, add two ciphers, and divide by 8.
To find the value of any number of articles at 75 cents each, deduct one-quarter of the number from itself and call the remainder dollars.
To Subtract Any Number Consisting of Two Figures from 100.
Take the first figure from 9, and the second from 10. For example: in subtracting 73 from 100, or in taking 73 cents change out of a dollar, say 7 from 9 and 2, and 3 from 10 and 7, or 27 cents. Practice this rule. It is simple, and will be found particularly helpful in making change.
Divisions.
A number is divisible by 2 when the last digit is even.
A number is divisible by 4 when the last two digits are divisible by 4.
To divide by 12 1/2, multiply by 8, and cut off two figures.
Simple Discount Rule.
This simple rule is in use in many houses where several discounts are allowed from list prices. Suppose the list price of a piano to be $500, and you allow an agent 25, 20 and 10 off.