OK, let's crack this. We're given 945 and our task is to multiply it by 4. Essentially, we'll be adding 945 to itself 4 times.
Step 1: 0 + 945 = 945
Step 2: 945 + 945 = 1890
Step 3: 1890 + 945 = 2835
Step 4: 2835 + 945 = 3780

So, 945*4 = 3780