How many 1’s are present in the binary representation of 15×256 + 5×16 + 3:

First, recognize that 256 = 162.

The expression becomes 15×256 + 5×16 + 3, which corresponds to the hexadecimal number (F53)16.

Convert each hex digit to its 4-bit binary equivalent: F is 1111, 5 is 0101, and 3 is 0011.

Counting the set bits gives 4+2+2 = 8 ones in total.