Without delay, let's solve this. We've got 645 and we will be multiplying it by 70, that is, adding 645 to itself 70 times.
Step 1: 0 + 645 = 645
Step 2: 645 + 645 = 1290
Step 3: 1290 + 645 = 1935
Step 4: 1935 + 645 = 2580
Step 5: 2580 + 645 = 3225
Step 6: 3225 + 645 = 3870
Step 7: 3870 + 645 = 4515
Step 8: 4515 + 645 = 5160
Step 9: 5160 + 645 = 5805
Step 10: 5805 + 645 = 6450
Step 11: 6450 + 645 = 7095
Step 12: 7095 + 645 = 7740
Step 13: 7740 + 645 = 8385
Step 14: 8385 + 645 = 9030
Step 15: 9030 + 645 = 9675
Step 16: 9675 + 645 = 10320
Step 17: 10320 + 645 = 10965
Step 18: 10965 + 645 = 11610
Step 19: 11610 + 645 = 12255
Step 20: 12255 + 645 = 12900
Step 21: 12900 + 645 = 13545
Step 22: 13545 + 645 = 14190
Step 23: 14190 + 645 = 14835
Step 24: 14835 + 645 = 15480
Step 25: 15480 + 645 = 16125
Step 26: 16125 + 645 = 16770
Step 27: 16770 + 645 = 17415
Step 28: 17415 + 645 = 18060
Step 29: 18060 + 645 = 18705
Step 30: 18705 + 645 = 19350
Step 31: 19350 + 645 = 19995
Step 32: 19995 + 645 = 20640
Step 33: 20640 + 645 = 21285
Step 34: 21285 + 645 = 21930
Step 35: 21930 + 645 = 22575
Step 36: 22575 + 645 = 23220
Step 37: 23220 + 645 = 23865
Step 38: 23865 + 645 = 24510
Step 39: 24510 + 645 = 25155
Step 40: 25155 + 645 = 25800
Step 41: 25800 + 645 = 26445
Step 42: 26445 + 645 = 27090
Step 43: 27090 + 645 = 27735
Step 44: 27735 + 645 = 28380
Step 45: 28380 + 645 = 29025
Step 46: 29025 + 645 = 29670
Step 47: 29670 + 645 = 30315
Step 48: 30315 + 645 = 30960
Step 49: 30960 + 645 = 31605
Step 50: 31605 + 645 = 32250
Step 51: 32250 + 645 = 32895
Step 52: 32895 + 645 = 33540
Step 53: 33540 + 645 = 34185
Step 54: 34185 + 645 = 34830
Step 55: 34830 + 645 = 35475
Step 56: 35475 + 645 = 36120
Step 57: 36120 + 645 = 36765
Step 58: 36765 + 645 = 37410
Step 59: 37410 + 645 = 38055
Step 60: 38055 + 645 = 38700
Step 61: 38700 + 645 = 39345
Step 62: 39345 + 645 = 39990
Step 63: 39990 + 645 = 40635
Step 64: 40635 + 645 = 41280
Step 65: 41280 + 645 = 41925
Step 66: 41925 + 645 = 42570
Step 67: 42570 + 645 = 43215
Step 68: 43215 + 645 = 43860
Step 69: 43860 + 645 = 44505
Step 70: 44505 + 645 = 45150

So, 645*70 = 45150