Conversion of decimal number 55 into binary is:
55 / 2 = 27 with remainder 1
27 / 2 = 13 with remainder 1
13 / 2 = 6 with remainder 1
6 / 2 = 3 with remainder 0
3 / 2 = 1 with remainder 1
1 / 2 = 0 with remainder 1
Hence, the decimal number 55 in binary is 110111.