Multiplication of 2 numbers that are near to 100 or 1000

Friday, January 16th, 2009
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This tip is suitable for multiplying two numbers that are near to 100. For example, 103 x 104 and 97 x 98.

Example 1:

To calculate 103 x 104:

  1. Add the the ones from the multiplicand to the multiplier.
    103 + 4 = 107.
  2. Multiply the ones from the multiplier with the ones from the multiplicand.
    3 x 4 = 12.
  3. Concatenate the results from step 1 and 2. Therefore, 103 x 104 = 10712.

Example 2:

To calculate 1005 x 1002:

  1. Add the the ones from the multiplicand to the multiplier.
    1005 + 2 = 1007.
  2. Multiply the ones from the multiplier with the ones from the multiplicand. Prepend a zero to the result.
    5 x 1 = 010.
  3. Concatenate the results from step 1 and 2. Therefore, 1005 x 1002 = 1007010.

Example 3:

To calculate 97 x 98:

  1. Subtract from 10, the ones from multiplicand.
    10 – 8 = 2.
  2. Subtract from multiplier, the result from step 1.
    97 – 2 = 95.
  3. Subtract from 10, the ones from multiplier.
    10 – 7 = 3.
  4. Multiply the result from step 3 with the result from 1. Prepend a zero.
    2 x 3 = 06.
  5. Concatenate the results from step 2 and step 4. Therefore, 97 x 98 = 9506.

Example 4:

To calculate 993 x 995:

  1. Subtract from 10, the ones from multiplicand.
    10 – 5 = 5.
  2. Subtract from multiplier, the result from step 1.
    993 – 5 = 988.
  3. Subtract from 10, the ones from multiplier.
    10 – 3 = 7.
  4. Multiply the result from step 3 with the result from 1. If you get a one digit number, prepend two zeroes, otherwise prepend just one zero.
    5 x 7 = 035.
  5. Concatenate the results from step 2 and step 4. Therefore, 993 x 995 = 988035.

Exercise:

If domain name is cost $9.90 each, what is the cost if you want to buy 92 domain?

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5 Responses to “Multiplication of 2 numbers that are near to 100 or 1000”

  1. KH says:

    Great technique! Very useful today where most of the prices around end with 9-something(eg 9.99, 9.97).

    KHs last blog post..Words from The Old Man

  2. KNizam says:

    perghhhhhhhhhhh neh betul2 minimalist neh.
    hehe i like !

  3. A Vedic matrix 0…9 is given below!

    ..0…..1…..2…..3…..4…..5…..6…..7…..8…..9
    —– —– —– —– —– —– —– —– —– —–
    0
    —– —– —– —– —– —– —– —– —– —–
    1
    —– —– —– —– —– —– —– —– —– —–
    2
    —– —– —– —– —– —– —– —– —– —–
    3
    —– —– —– —– —– —– —– —– —– —–
    4
    —– —– —– —– —– —– —– —– —– —–
    5
    —– —– —– —– —– —– —– —– —– —–
    6
    —– —– —– —– —– —– —– —– —– —–
    7
    —– —– —– —– —– —– —– —– —– —–
    8
    —– —– —– —– —– —– —– —– —– —–
    9…………………………………….97

    97 is ‘3 less than’ a 100. It means (+97-3) position
    89 is ‘11 less tham’ a 100. It means(+89-11) position’

    See that 97-11= 86 and 89-3= 86
    Merge (-3)*(-11)= 33 to right of 86 as 8633.
    97*89= 8633

  4. .0….1….2….3….4….5….6….7….8….9
    —– —– —– —– —– —– —– —– —– —–
    0
    —– —– —– —– —– —– —– —– —– —–
    1
    —– —– —– —– —– —– —– —– —– —–
    2
    —– —– —– —– —– —– —– —– —– —–
    3
    —– —– —– —– —– —– —– —– —– —–
    4
    —– —– —– —– —– —– —– —– —– —–
    5
    —– —– —– —– —– —– —– —– —– —–
    6
    —– —– —– —– —– —– —– —– —– —–
    7
    —– —– —– —– —– —– —– —– —– —–
    8
    —– —– —– —– —– —– —– 97 —– —–
    9

    97 is a position that has 97 ones before it.
    So (+97-3)is written!
    89 is (+89-11)!
    Basics shall be correct!

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