OK, let's work through this together. We're starting with 4 and we're going to multiply it by 16, which means we add 4 to itself 16 times.
Step 1: 0 + 4 = 4
Step 2: 4 + 4 = 8
Step 3: 8 + 4 = 12
Step 4: 12 + 4 = 16
Step 5: 16 + 4 = 20
Step 6: 20 + 4 = 24
Step 7: 24 + 4 = 28
Step 8: 28 + 4 = 32
Step 9: 32 + 4 = 36
Step 10: 36 + 4 = 40
Step 11: 40 + 4 = 44
Step 12: 44 + 4 = 48
Step 13: 48 + 4 = 52
Step 14: 52 + 4 = 56
Step 15: 56 + 4 = 60
Step 16: 60 + 4 = 64

So, 4*16 = 64