By a little practice any one may become as familiar with this rule and as ready in its application as with the ordinary method.
To multiply any number by 2 1/2, add one cipher, and divide by 4.
To multiply any number by 3 1/3, add one cipher, and divide by 3.
To multiply by 33 1/3, add two ciphers, and divide by 3.
To multiply any number by 1 3/7, add one cipher, and divide by 7.
To multiply by 16 2/3, add two ciphers, and divide by 6.
To multiply by 14 2/7, add two ciphers, and divide by 7.
To multiply by 875, add three ciphers, and divide by 8.
To divide by 25, multiply by 4, and cut off two figures.
To divide by 125, multiply by 8, and cut off three figures.