Why Electricity is Being transmitted in multiple of 11

Why electricity is being transmitted in multiple of 11 ?

There is no real standard around the world and many countries use different voltage levels for their purpose.

I found one  statement  from a standard electrical text book  

[So that the answer is quite simple in that when one designs motor and transformer and even instrumentation, one finds that such equipment respond to the average value of voltage, current and flux. As  such transformers are normally designed to have an integer value for  voltage/turn  OR Ampere-turn.

In such cases the average value will be 10,30,60_ _ _ _ Kv and if one multiplies by 1.11 which is the  form factor for a sinusoidal wave one will get 11,33,66 Kv etc. Generally the number after the first two digits are just ignored

The above answer is not correct why because 

Right Answer is 
When we want to maintain 10Kv at receiving end, transmission companies transfer 10% extra then receiving end voltage. i.e. 11kv, similarly 10% 20,30,60,120. i.e. 33kv, 66kv, 132kv

Now a day we are using 400v  instead of 440v , 230v instead of  220v
also alternators also available which can generate voltage level in the range of 10.5kv to 15.5kv so generation in multiple of 11 does not arise.

Key Wards:

Why transmission line 11kv or 33kv 66kv 

what is 11kv electrical system

why generation voltage is 11kv

why ac voltage is multiple of 11

why the level of the voltage in transmission are multiples of 11 is there any technical reason 

why do we use ac and not dc system in India ?

why the transformer voltage is always in the multiple of 11