Warp Mass :: Multiplication Tricks Summary - (2)

The multiplication of two numbers spaced far from a power of 10

If you follow me, then you can solve all the problems below.
Only will one more modified process be added.

• 48 X 53 = ?

1. The base shall be 5 X 10.
2. You shall subtract 50 each from 48 and 53, which would be -2, +3.
3. You shall position the numbers like the followed.
4. On the left, you shall position the value of 48 + 3 or 53 + (-2) which is the diagonal summation and multiply the value by 5.
   Don't forget to multiply the value by 5.
5. On the right, you shall position the value of (-2) X 3.
   The digits on the right must be equal to the number of zeros in base.

       48          -2
       53         +3
    --------------------
       51    |  
    X  5    |  
    --------------------
     255    |    -06
    --------------------
     255-1 |  10-06
    --------------------
        254  |   04

Do Exercise

• 7012 X 6998 = ?
   Base : 7 X 1,000
    7012           012
    6998          -002
   ----------------------------
    7010     |
    X    7     |  
   ----------------------------
   49070    |     -024
   ----------------------------
   49070-1 |  1000-024
   ----------------------------
   49069    |      976

ANOTHER TRICKS for 99, 999, 9999, · · ·

• 16 X 99 = ?
  
  

1. You subtract 1 from the number other than 99, 999, 999, · · ·.
   → 16 - 1 = 15
2. On the left, you shall position 15.
3. You subtract this value from 99,999,999, · · ·.
   → 99 - 15 = 84
4. On the right, you shall position 84.
   The digits on the right must be equal to the number of nines in 99, 999, 9999, · · ·.

           16
    X    99
    ------------
      15  |  84

Do Exercise

• 49625 X 99999

            49625
      X   99999
 -------------------------
     49624  |  50375

• 3452 X 99999

              3452
      X   99999
 -------------------------
     3452  |  96457

• 45237 X 999
  → If the digits of the number other than 99, 999, · · ·, is longer than 99, 999, · · ·
  → You convert 999 into (1000-1)
  → 45237 X (1000-1)
  → 45237000-45237
  → 45191763