Multiplication of two numbers which one of the number is close to 100 (55 x 95).



Multiplication of two numbers less than 100.

Condition:

Multiplication of two numbers, one of them must be close to 100. Preferably, the other one is a double digit number.

Example 1:
55 x 95 = ?

Steps:
  1. Find the 100's complement of the two numbers. For example, 55 is 45 less than 100, hence we put its complement as -45, and with the same method, the complement of 95 is -5.
  2. We add the multiplicand to the complement of the multiplier or add the multiplier to the complement of the multiplicand. (You should always get the same answer for both.) Multiply the answer obtained 100. In this case, (55 - 5) x 100 = 5000
  3. Find the product of the two complement numbers (in this case, -45 and -5). Add this number to the number that you obtained in step 2.
  4. And we get the answer. 55 x 95 = 5225

Example 2:
23 x 99 = ?
100's complement of the two numbers:
23 → -77
99 → -1

(23 - 1) x 100 = 2200

Product of the complements:
(-77) x (-1) = 77

23 x 99 = 2200 + 77 = 2277

Example 3:
67 x 98 = ?

100's complement of the two numbers:
67 → -33
98 → -2

(67 - 2) x 100 = 6500

Product of the complements:
(-33) x (-2) = 66

67 x 98 = 6500 + 66 6566

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