(55)10

solution:

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.