Some special case in multiplication

  1. Multiplying two numbers whose difference is
    10 and unit digit is 5
    )
    Example - 25 * 35
    First categories in two parts
    In first part
    2, 3: big number square subtract 1
    3^2 - 1 = 9 - 1 = 8
    In second part
    Always put 75
    So answer became 875

Example - 155 * 165
= 256 - 1 | 75
= 25575

Dear Raja,

You are on a roll!
Again; great technique for these kinds of multiplications.

If I see 25 * 35, I immediately change to 30^2 - 5^2.
using: (a+b)(a-b) = a^2 - b^2

btw, hope you don’t mind me editing your post for readability.
On this forum you can use Latex commands.
So type $(a+b)(a-b) = a^2 - b^2$ to get:
(a+b)(a-b) = a^2 - b^2

If questions is different from them then
Example - 255 * 265
How you do that?

Same way. The middle point between 255 and 265 is 260.
So for:

use a = 260 & b = 5. So:
260^2 - 5^2 = 67600 - 25 = 67575

The way of working is exactly the same. I take 26, square it, add two zeros, then subtract 25 (which is the same as your subtract one and concatenate 75).

But you can easily answer this type of questions with my method
Ex- 265 * 255
676-1 | 75
67575

Like I said;