Let's roll up our sleeves and solve this. We have 1000 and we're going to multiply it by 13, essentially adding 1000 to itself 13 times.
Step 1: 0 + 1000 = 1000
Step 2: 1000 + 1000 = 2000
Step 3: 2000 + 1000 = 3000
Step 4: 3000 + 1000 = 4000
Step 5: 4000 + 1000 = 5000
Step 6: 5000 + 1000 = 6000
Step 7: 6000 + 1000 = 7000
Step 8: 7000 + 1000 = 8000
Step 9: 8000 + 1000 = 9000
Step 10: 9000 + 1000 = 10000
Step 11: 10000 + 1000 = 11000
Step 12: 11000 + 1000 = 12000
Step 13: 12000 + 1000 = 13000

So, 1000*13 = 13000