Let's get this math done. We have 625 and we're going to multiply it by 31. This is the same as taking 625 and adding it to itself 31 times.
Step 1: 0 + 625 = 625
Step 2: 625 + 625 = 1250
Step 3: 1250 + 625 = 1875
Step 4: 1875 + 625 = 2500
Step 5: 2500 + 625 = 3125
Step 6: 3125 + 625 = 3750
Step 7: 3750 + 625 = 4375
Step 8: 4375 + 625 = 5000
Step 9: 5000 + 625 = 5625
Step 10: 5625 + 625 = 6250
Step 11: 6250 + 625 = 6875
Step 12: 6875 + 625 = 7500
Step 13: 7500 + 625 = 8125
Step 14: 8125 + 625 = 8750
Step 15: 8750 + 625 = 9375
Step 16: 9375 + 625 = 10000
Step 17: 10000 + 625 = 10625
Step 18: 10625 + 625 = 11250
Step 19: 11250 + 625 = 11875
Step 20: 11875 + 625 = 12500
Step 21: 12500 + 625 = 13125
Step 22: 13125 + 625 = 13750
Step 23: 13750 + 625 = 14375
Step 24: 14375 + 625 = 15000
Step 25: 15000 + 625 = 15625
Step 26: 15625 + 625 = 16250
Step 27: 16250 + 625 = 16875
Step 28: 16875 + 625 = 17500
Step 29: 17500 + 625 = 18125
Step 30: 18125 + 625 = 18750
Step 31: 18750 + 625 = 19375

So, 625*31 = 19375