They aren't in all cases. 110 volts is nominal and may range from 110 to 120 in a typical residence.
Transmission voltages are in multiples of 11 to allow for 10% transmission line losses. Therefore, to obtain 100% efficiency, voltages in multiples of 11 are transmitted.
In the metric system, measurements are expressed in multiples of 10.
11,22,33,44,55,66,77,88,99,110,121,131,141,151,161,171,181,191,202,
First eleven multiples of 4 are 4, 8, 12, 16, 20, 24, 28, 32, 36, 40 & 44.
Any multiple of 110.
Expressed as a decimal fraction, 11/15 is equal to 0.73 recurring (that is, 0.73333...)
11, 22, 33, 44, and 55 are the first five multiples for eleven
Expressed in words, this is equal to eleven million.
99, 198, 297, 396, 495.
11 millionths is expressed as 0.000011 in decimal form.
Expressed in figures, this is equal to 1011000.
Expressed as a decimal, 11/20 is equal to 0.55.