OK, let's crack this. We're given 280 and our task is to multiply it by 5. Essentially, we'll be adding 280 to itself 5 times.
Step 1: 0 + 280 = 280
Step 2: 280 + 280 = 560
Step 3: 560 + 280 = 840
Step 4: 840 + 280 = 1120
Step 5: 1120 + 280 = 1400

So, 280*5 = 1400