Let's get this math done. We have 320 and we're going to multiply it by 135. This is the same as taking 320 and adding it to itself 135 times.
Step 1: 0 + 320 = 320
Step 2: 320 + 320 = 640
Step 3: 640 + 320 = 960
Step 4: 960 + 320 = 1280
Step 5: 1280 + 320 = 1600
Step 6: 1600 + 320 = 1920
Step 7: 1920 + 320 = 2240
Step 8: 2240 + 320 = 2560
Step 9: 2560 + 320 = 2880
Step 10: 2880 + 320 = 3200
Step 11: 3200 + 320 = 3520
Step 12: 3520 + 320 = 3840
Step 13: 3840 + 320 = 4160
Step 14: 4160 + 320 = 4480
Step 15: 4480 + 320 = 4800
Step 16: 4800 + 320 = 5120
Step 17: 5120 + 320 = 5440
Step 18: 5440 + 320 = 5760
Step 19: 5760 + 320 = 6080
Step 20: 6080 + 320 = 6400
Step 21: 6400 + 320 = 6720
Step 22: 6720 + 320 = 7040
Step 23: 7040 + 320 = 7360
Step 24: 7360 + 320 = 7680
Step 25: 7680 + 320 = 8000
Step 26: 8000 + 320 = 8320
Step 27: 8320 + 320 = 8640
Step 28: 8640 + 320 = 8960
Step 29: 8960 + 320 = 9280
Step 30: 9280 + 320 = 9600
Step 31: 9600 + 320 = 9920
Step 32: 9920 + 320 = 10240
Step 33: 10240 + 320 = 10560
Step 34: 10560 + 320 = 10880
Step 35: 10880 + 320 = 11200
Step 36: 11200 + 320 = 11520
Step 37: 11520 + 320 = 11840
Step 38: 11840 + 320 = 12160
Step 39: 12160 + 320 = 12480
Step 40: 12480 + 320 = 12800
Step 41: 12800 + 320 = 13120
Step 42: 13120 + 320 = 13440
Step 43: 13440 + 320 = 13760
Step 44: 13760 + 320 = 14080
Step 45: 14080 + 320 = 14400
Step 46: 14400 + 320 = 14720
Step 47: 14720 + 320 = 15040
Step 48: 15040 + 320 = 15360
Step 49: 15360 + 320 = 15680
Step 50: 15680 + 320 = 16000
Step 51: 16000 + 320 = 16320
Step 52: 16320 + 320 = 16640
Step 53: 16640 + 320 = 16960
Step 54: 16960 + 320 = 17280
Step 55: 17280 + 320 = 17600
Step 56: 17600 + 320 = 17920
Step 57: 17920 + 320 = 18240
Step 58: 18240 + 320 = 18560
Step 59: 18560 + 320 = 18880
Step 60: 18880 + 320 = 19200
Step 61: 19200 + 320 = 19520
Step 62: 19520 + 320 = 19840
Step 63: 19840 + 320 = 20160
Step 64: 20160 + 320 = 20480
Step 65: 20480 + 320 = 20800
Step 66: 20800 + 320 = 21120
Step 67: 21120 + 320 = 21440
Step 68: 21440 + 320 = 21760
Step 69: 21760 + 320 = 22080
Step 70: 22080 + 320 = 22400
Step 71: 22400 + 320 = 22720
Step 72: 22720 + 320 = 23040
Step 73: 23040 + 320 = 23360
Step 74: 23360 + 320 = 23680
Step 75: 23680 + 320 = 24000
Step 76: 24000 + 320 = 24320
Step 77: 24320 + 320 = 24640
Step 78: 24640 + 320 = 24960
Step 79: 24960 + 320 = 25280
Step 80: 25280 + 320 = 25600
Step 81: 25600 + 320 = 25920
Step 82: 25920 + 320 = 26240
Step 83: 26240 + 320 = 26560
Step 84: 26560 + 320 = 26880
Step 85: 26880 + 320 = 27200
Step 86: 27200 + 320 = 27520
Step 87: 27520 + 320 = 27840
Step 88: 27840 + 320 = 28160
Step 89: 28160 + 320 = 28480
Step 90: 28480 + 320 = 28800
Step 91: 28800 + 320 = 29120
Step 92: 29120 + 320 = 29440
Step 93: 29440 + 320 = 29760
Step 94: 29760 + 320 = 30080
Step 95: 30080 + 320 = 30400
Step 96: 30400 + 320 = 30720
Step 97: 30720 + 320 = 31040
Step 98: 31040 + 320 = 31360
Step 99: 31360 + 320 = 31680
Step 100: 31680 + 320 = 32000
Step 101: 32000 + 320 = 32320
Step 102: 32320 + 320 = 32640
Step 103: 32640 + 320 = 32960
Step 104: 32960 + 320 = 33280
Step 105: 33280 + 320 = 33600
Step 106: 33600 + 320 = 33920
Step 107: 33920 + 320 = 34240
Step 108: 34240 + 320 = 34560
Step 109: 34560 + 320 = 34880
Step 110: 34880 + 320 = 35200
Step 111: 35200 + 320 = 35520
Step 112: 35520 + 320 = 35840
Step 113: 35840 + 320 = 36160
Step 114: 36160 + 320 = 36480
Step 115: 36480 + 320 = 36800
Step 116: 36800 + 320 = 37120
Step 117: 37120 + 320 = 37440
Step 118: 37440 + 320 = 37760
Step 119: 37760 + 320 = 38080
Step 120: 38080 + 320 = 38400
Step 121: 38400 + 320 = 38720
Step 122: 38720 + 320 = 39040
Step 123: 39040 + 320 = 39360
Step 124: 39360 + 320 = 39680
Step 125: 39680 + 320 = 40000
Step 126: 40000 + 320 = 40320
Step 127: 40320 + 320 = 40640
Step 128: 40640 + 320 = 40960
Step 129: 40960 + 320 = 41280
Step 130: 41280 + 320 = 41600
Step 131: 41600 + 320 = 41920
Step 132: 41920 + 320 = 42240
Step 133: 42240 + 320 = 42560
Step 134: 42560 + 320 = 42880
Step 135: 42880 + 320 = 43200

So, 320*135 = 43200