Let's roll up our sleeves and solve this. We have 10 and we're going to multiply it by 31, essentially adding 10 to itself 31 times.
Step 1: 0 + 10 = 10
Step 2: 10 + 10 = 20
Step 3: 20 + 10 = 30
Step 4: 30 + 10 = 40
Step 5: 40 + 10 = 50
Step 6: 50 + 10 = 60
Step 7: 60 + 10 = 70
Step 8: 70 + 10 = 80
Step 9: 80 + 10 = 90
Step 10: 90 + 10 = 100
Step 11: 100 + 10 = 110
Step 12: 110 + 10 = 120
Step 13: 120 + 10 = 130
Step 14: 130 + 10 = 140
Step 15: 140 + 10 = 150
Step 16: 150 + 10 = 160
Step 17: 160 + 10 = 170
Step 18: 170 + 10 = 180
Step 19: 180 + 10 = 190
Step 20: 190 + 10 = 200
Step 21: 200 + 10 = 210
Step 22: 210 + 10 = 220
Step 23: 220 + 10 = 230
Step 24: 230 + 10 = 240
Step 25: 240 + 10 = 250
Step 26: 250 + 10 = 260
Step 27: 260 + 10 = 270
Step 28: 270 + 10 = 280
Step 29: 280 + 10 = 290
Step 30: 290 + 10 = 300
Step 31: 300 + 10 = 310

So, 10*31 = 310