Let's roll up our sleeves and solve this. We have 625 and we're going to multiply it by 4, essentially adding 625 to itself 4 times.
Step 1: 0 + 625 = 625
Step 2: 625 + 625 = 1250
Step 3: 1250 + 625 = 1875
Step 4: 1875 + 625 = 2500

So, 625*4 = 2500