Let's roll up our sleeves and solve this. We have 620 and we're going to multiply it by 65, essentially adding 620 to itself 65 times.
Step 1: 0 + 620 = 620
Step 2: 620 + 620 = 1240
Step 3: 1240 + 620 = 1860
Step 4: 1860 + 620 = 2480
Step 5: 2480 + 620 = 3100
Step 6: 3100 + 620 = 3720
Step 7: 3720 + 620 = 4340
Step 8: 4340 + 620 = 4960
Step 9: 4960 + 620 = 5580
Step 10: 5580 + 620 = 6200
Step 11: 6200 + 620 = 6820
Step 12: 6820 + 620 = 7440
Step 13: 7440 + 620 = 8060
Step 14: 8060 + 620 = 8680
Step 15: 8680 + 620 = 9300
Step 16: 9300 + 620 = 9920
Step 17: 9920 + 620 = 10540
Step 18: 10540 + 620 = 11160
Step 19: 11160 + 620 = 11780
Step 20: 11780 + 620 = 12400
Step 21: 12400 + 620 = 13020
Step 22: 13020 + 620 = 13640
Step 23: 13640 + 620 = 14260
Step 24: 14260 + 620 = 14880
Step 25: 14880 + 620 = 15500
Step 26: 15500 + 620 = 16120
Step 27: 16120 + 620 = 16740
Step 28: 16740 + 620 = 17360
Step 29: 17360 + 620 = 17980
Step 30: 17980 + 620 = 18600
Step 31: 18600 + 620 = 19220
Step 32: 19220 + 620 = 19840
Step 33: 19840 + 620 = 20460
Step 34: 20460 + 620 = 21080
Step 35: 21080 + 620 = 21700
Step 36: 21700 + 620 = 22320
Step 37: 22320 + 620 = 22940
Step 38: 22940 + 620 = 23560
Step 39: 23560 + 620 = 24180
Step 40: 24180 + 620 = 24800
Step 41: 24800 + 620 = 25420
Step 42: 25420 + 620 = 26040
Step 43: 26040 + 620 = 26660
Step 44: 26660 + 620 = 27280
Step 45: 27280 + 620 = 27900
Step 46: 27900 + 620 = 28520
Step 47: 28520 + 620 = 29140
Step 48: 29140 + 620 = 29760
Step 49: 29760 + 620 = 30380
Step 50: 30380 + 620 = 31000
Step 51: 31000 + 620 = 31620
Step 52: 31620 + 620 = 32240
Step 53: 32240 + 620 = 32860
Step 54: 32860 + 620 = 33480
Step 55: 33480 + 620 = 34100
Step 56: 34100 + 620 = 34720
Step 57: 34720 + 620 = 35340
Step 58: 35340 + 620 = 35960
Step 59: 35960 + 620 = 36580
Step 60: 36580 + 620 = 37200
Step 61: 37200 + 620 = 37820
Step 62: 37820 + 620 = 38440
Step 63: 38440 + 620 = 39060
Step 64: 39060 + 620 = 39680
Step 65: 39680 + 620 = 40300

So, 620*65 = 40300