Manostaxx
The text that follows is owned by the site above referred.
Here is only a small part of the article, for more please follow the link
SOURCE: https://www.easycalculation.com/math-facts/multiplication-shortcut-for-two-digit-numbers.html
This trick can be applied when
– First digit of both the numbers (multiplicand and multiplier) are same.
– Sum of their second digits equals 10.
Example: 23 x 27
In the above example, as first digit of both the numbers are 2 and sum on second digits (3+7) is 10 we can use this trick.
Follow the simple steps to learn the shortcut trick
Step 1: Take the first digit, add it with one and multiply the resultant value with the same.
= (2+1) x 2 = 6
Step 2: Multiply the second digits of both the numbers.
= 3×7 = 21
Step 3: Now join and write the step 1 and step 2 result together. That is the answer. So 23 x 27 = 621
With few more examples,
Example 1: 92 x 98
(9 + 1) x 9 = 90
2 x 8 = 16
Answer is 92 x 98 = 9016
Example 2: 77 x 73
(7 + 1) x 7 = 56
7 x 3 = 21
Answer is 77 x 73 = 5621
Example 3: 85 x 85
(8 + 1) x 8 = 72
5 x 5 = 25
Answer is 85 x 85 = 7225
