To multiply by 1001, add three ciphers to the multiplicand, and add to this the multiplicand.
To Multiply by 5, 25, 125.
To multiply by 5, add a cipher and divide by 2.
To multiply by 25, add two ciphers and divide by 4.
To multiply by 125, add three ciphers and divide by 8.
Another Easy Way to Multiply.
| 82 |
| 54 |
| 4428 |
To multiply two figures by two figures, proceed as follows: Multiply units by units for the first figure.
Carry and multiply tens by units and units by tens, (adding) for the second figure. Carry and multiply tens by tens for the remaining figure or figures. In this example proceed as follows:
2 × 4 = 8 = 1st figure.
(4 × 8) + (5 × 2) = 42. Therefore 2 = 2d figure.
(5 × 8) + 4 carried = 44 = 3d and 4th figures.