OK, let's work through this together. We're starting with 646 and we're going to multiply it by 70, which means we add 646 to itself 70 times.
Step 1: 0 + 646 = 646
Step 2: 646 + 646 = 1292
Step 3: 1292 + 646 = 1938
Step 4: 1938 + 646 = 2584
Step 5: 2584 + 646 = 3230
Step 6: 3230 + 646 = 3876
Step 7: 3876 + 646 = 4522
Step 8: 4522 + 646 = 5168
Step 9: 5168 + 646 = 5814
Step 10: 5814 + 646 = 6460
Step 11: 6460 + 646 = 7106
Step 12: 7106 + 646 = 7752
Step 13: 7752 + 646 = 8398
Step 14: 8398 + 646 = 9044
Step 15: 9044 + 646 = 9690
Step 16: 9690 + 646 = 10336
Step 17: 10336 + 646 = 10982
Step 18: 10982 + 646 = 11628
Step 19: 11628 + 646 = 12274
Step 20: 12274 + 646 = 12920
Step 21: 12920 + 646 = 13566
Step 22: 13566 + 646 = 14212
Step 23: 14212 + 646 = 14858
Step 24: 14858 + 646 = 15504
Step 25: 15504 + 646 = 16150
Step 26: 16150 + 646 = 16796
Step 27: 16796 + 646 = 17442
Step 28: 17442 + 646 = 18088
Step 29: 18088 + 646 = 18734
Step 30: 18734 + 646 = 19380
Step 31: 19380 + 646 = 20026
Step 32: 20026 + 646 = 20672
Step 33: 20672 + 646 = 21318
Step 34: 21318 + 646 = 21964
Step 35: 21964 + 646 = 22610
Step 36: 22610 + 646 = 23256
Step 37: 23256 + 646 = 23902
Step 38: 23902 + 646 = 24548
Step 39: 24548 + 646 = 25194
Step 40: 25194 + 646 = 25840
Step 41: 25840 + 646 = 26486
Step 42: 26486 + 646 = 27132
Step 43: 27132 + 646 = 27778
Step 44: 27778 + 646 = 28424
Step 45: 28424 + 646 = 29070
Step 46: 29070 + 646 = 29716
Step 47: 29716 + 646 = 30362
Step 48: 30362 + 646 = 31008
Step 49: 31008 + 646 = 31654
Step 50: 31654 + 646 = 32300
Step 51: 32300 + 646 = 32946
Step 52: 32946 + 646 = 33592
Step 53: 33592 + 646 = 34238
Step 54: 34238 + 646 = 34884
Step 55: 34884 + 646 = 35530
Step 56: 35530 + 646 = 36176
Step 57: 36176 + 646 = 36822
Step 58: 36822 + 646 = 37468
Step 59: 37468 + 646 = 38114
Step 60: 38114 + 646 = 38760
Step 61: 38760 + 646 = 39406
Step 62: 39406 + 646 = 40052
Step 63: 40052 + 646 = 40698
Step 64: 40698 + 646 = 41344
Step 65: 41344 + 646 = 41990
Step 66: 41990 + 646 = 42636
Step 67: 42636 + 646 = 43282
Step 68: 43282 + 646 = 43928
Step 69: 43928 + 646 = 44574
Step 70: 44574 + 646 = 45220

So, 646*70 = 45220