Let's roll up our sleeves and solve this. We have 400 and we're going to multiply it by 5, essentially adding 400 to itself 5 times.
Step 1: 0 + 400 = 400
Step 2: 400 + 400 = 800
Step 3: 800 + 400 = 1200
Step 4: 1200 + 400 = 1600
Step 5: 1600 + 400 = 2000

So, 400*5 = 2000