OK, let's crack this. We're given 640 and our task is to multiply it by 53. Essentially, we'll be adding 640 to itself 53 times.
Step 1: 0 + 640 = 640
Step 2: 640 + 640 = 1280
Step 3: 1280 + 640 = 1920
Step 4: 1920 + 640 = 2560
Step 5: 2560 + 640 = 3200
Step 6: 3200 + 640 = 3840
Step 7: 3840 + 640 = 4480
Step 8: 4480 + 640 = 5120
Step 9: 5120 + 640 = 5760
Step 10: 5760 + 640 = 6400
Step 11: 6400 + 640 = 7040
Step 12: 7040 + 640 = 7680
Step 13: 7680 + 640 = 8320
Step 14: 8320 + 640 = 8960
Step 15: 8960 + 640 = 9600
Step 16: 9600 + 640 = 10240
Step 17: 10240 + 640 = 10880
Step 18: 10880 + 640 = 11520
Step 19: 11520 + 640 = 12160
Step 20: 12160 + 640 = 12800
Step 21: 12800 + 640 = 13440
Step 22: 13440 + 640 = 14080
Step 23: 14080 + 640 = 14720
Step 24: 14720 + 640 = 15360
Step 25: 15360 + 640 = 16000
Step 26: 16000 + 640 = 16640
Step 27: 16640 + 640 = 17280
Step 28: 17280 + 640 = 17920
Step 29: 17920 + 640 = 18560
Step 30: 18560 + 640 = 19200
Step 31: 19200 + 640 = 19840
Step 32: 19840 + 640 = 20480
Step 33: 20480 + 640 = 21120
Step 34: 21120 + 640 = 21760
Step 35: 21760 + 640 = 22400
Step 36: 22400 + 640 = 23040
Step 37: 23040 + 640 = 23680
Step 38: 23680 + 640 = 24320
Step 39: 24320 + 640 = 24960
Step 40: 24960 + 640 = 25600
Step 41: 25600 + 640 = 26240
Step 42: 26240 + 640 = 26880
Step 43: 26880 + 640 = 27520
Step 44: 27520 + 640 = 28160
Step 45: 28160 + 640 = 28800
Step 46: 28800 + 640 = 29440
Step 47: 29440 + 640 = 30080
Step 48: 30080 + 640 = 30720
Step 49: 30720 + 640 = 31360
Step 50: 31360 + 640 = 32000
Step 51: 32000 + 640 = 32640
Step 52: 32640 + 640 = 33280
Step 53: 33280 + 640 = 33920

So, 640*53 = 33920