OK, let's crack this. We're given 605 and our task is to multiply it by 4. Essentially, we'll be adding 605 to itself 4 times.
Step 1: 0 + 605 = 605
Step 2: 605 + 605 = 1210
Step 3: 1210 + 605 = 1815
Step 4: 1815 + 605 = 2420

So, 605*4 = 2420