OK, let's crack this. We're given 64 and our task is to multiply it by 4. Essentially, we'll be adding 64 to itself 4 times.
Step 1: 0 + 64 = 64
Step 2: 64 + 64 = 128
Step 3: 128 + 64 = 192
Step 4: 192 + 64 = 256

So, 64*4 = 256