Quick multiplication of any two digit number near to each other with help of algebraic close together method

We can utilize following algebraic identity for quick multiplication of any two digit number which are near to each other

(z + a) x (z + b) = z x (z + a + b) + a x b

Where, z = any number ends with zero.

For example,

To multiply 23 x 26,

Let, z = 20, a = 3, b = 6

So, 

(z + a) x (z + b) 

= z x (z + a + b) + a x b

= 20 x (20 + 3 + 6) + 3 x 6

= 20 x 29 + 3 x 6

= 580 + 18

= 598

Another example,

To multiply 88 x 86,

Let, z = 80, a = 8, b = 6

So, 

(z + a) x (z + b) 

= z x (z + a + b) + a x b

= 80 x (80 + 8 + 6) + 8 x 6

= 80 x 94 + 8 x 6

= 7520 + 48

= 7568