Answer
$28_{10}$ = $11100_{2}$
Work Step by Step
28$\div$2 = 14 remainder r[0] = 0
14$\div$2 = 7 remainder r[1] = 0
7$\div$2 = 3 remainder r[2] = 1
3$\div$2 = 1 remainder r[3] = 1
remainder r[4] = 1
$28_{10}$ = r[4]r[3]r[2]r[1]r[0] = 11100