OK, let's crack this. We're given 40 and our task is to multiply it by 172. Essentially, we'll be adding 40 to itself 172 times.
Step 1: 0 + 40 = 40
Step 2: 40 + 40 = 80
Step 3: 80 + 40 = 120
Step 4: 120 + 40 = 160
Step 5: 160 + 40 = 200
Step 6: 200 + 40 = 240
Step 7: 240 + 40 = 280
Step 8: 280 + 40 = 320
Step 9: 320 + 40 = 360
Step 10: 360 + 40 = 400
Step 11: 400 + 40 = 440
Step 12: 440 + 40 = 480
Step 13: 480 + 40 = 520
Step 14: 520 + 40 = 560
Step 15: 560 + 40 = 600
Step 16: 600 + 40 = 640
Step 17: 640 + 40 = 680
Step 18: 680 + 40 = 720
Step 19: 720 + 40 = 760
Step 20: 760 + 40 = 800
Step 21: 800 + 40 = 840
Step 22: 840 + 40 = 880
Step 23: 880 + 40 = 920
Step 24: 920 + 40 = 960
Step 25: 960 + 40 = 1000
Step 26: 1000 + 40 = 1040
Step 27: 1040 + 40 = 1080
Step 28: 1080 + 40 = 1120
Step 29: 1120 + 40 = 1160
Step 30: 1160 + 40 = 1200
Step 31: 1200 + 40 = 1240
Step 32: 1240 + 40 = 1280
Step 33: 1280 + 40 = 1320
Step 34: 1320 + 40 = 1360
Step 35: 1360 + 40 = 1400
Step 36: 1400 + 40 = 1440
Step 37: 1440 + 40 = 1480
Step 38: 1480 + 40 = 1520
Step 39: 1520 + 40 = 1560
Step 40: 1560 + 40 = 1600
Step 41: 1600 + 40 = 1640
Step 42: 1640 + 40 = 1680
Step 43: 1680 + 40 = 1720
Step 44: 1720 + 40 = 1760
Step 45: 1760 + 40 = 1800
Step 46: 1800 + 40 = 1840
Step 47: 1840 + 40 = 1880
Step 48: 1880 + 40 = 1920
Step 49: 1920 + 40 = 1960
Step 50: 1960 + 40 = 2000
Step 51: 2000 + 40 = 2040
Step 52: 2040 + 40 = 2080
Step 53: 2080 + 40 = 2120
Step 54: 2120 + 40 = 2160
Step 55: 2160 + 40 = 2200
Step 56: 2200 + 40 = 2240
Step 57: 2240 + 40 = 2280
Step 58: 2280 + 40 = 2320
Step 59: 2320 + 40 = 2360
Step 60: 2360 + 40 = 2400
Step 61: 2400 + 40 = 2440
Step 62: 2440 + 40 = 2480
Step 63: 2480 + 40 = 2520
Step 64: 2520 + 40 = 2560
Step 65: 2560 + 40 = 2600
Step 66: 2600 + 40 = 2640
Step 67: 2640 + 40 = 2680
Step 68: 2680 + 40 = 2720
Step 69: 2720 + 40 = 2760
Step 70: 2760 + 40 = 2800
Step 71: 2800 + 40 = 2840
Step 72: 2840 + 40 = 2880
Step 73: 2880 + 40 = 2920
Step 74: 2920 + 40 = 2960
Step 75: 2960 + 40 = 3000
Step 76: 3000 + 40 = 3040
Step 77: 3040 + 40 = 3080
Step 78: 3080 + 40 = 3120
Step 79: 3120 + 40 = 3160
Step 80: 3160 + 40 = 3200
Step 81: 3200 + 40 = 3240
Step 82: 3240 + 40 = 3280
Step 83: 3280 + 40 = 3320
Step 84: 3320 + 40 = 3360
Step 85: 3360 + 40 = 3400
Step 86: 3400 + 40 = 3440
Step 87: 3440 + 40 = 3480
Step 88: 3480 + 40 = 3520
Step 89: 3520 + 40 = 3560
Step 90: 3560 + 40 = 3600
Step 91: 3600 + 40 = 3640
Step 92: 3640 + 40 = 3680
Step 93: 3680 + 40 = 3720
Step 94: 3720 + 40 = 3760
Step 95: 3760 + 40 = 3800
Step 96: 3800 + 40 = 3840
Step 97: 3840 + 40 = 3880
Step 98: 3880 + 40 = 3920
Step 99: 3920 + 40 = 3960
Step 100: 3960 + 40 = 4000
Step 101: 4000 + 40 = 4040
Step 102: 4040 + 40 = 4080
Step 103: 4080 + 40 = 4120
Step 104: 4120 + 40 = 4160
Step 105: 4160 + 40 = 4200
Step 106: 4200 + 40 = 4240
Step 107: 4240 + 40 = 4280
Step 108: 4280 + 40 = 4320
Step 109: 4320 + 40 = 4360
Step 110: 4360 + 40 = 4400
Step 111: 4400 + 40 = 4440
Step 112: 4440 + 40 = 4480
Step 113: 4480 + 40 = 4520
Step 114: 4520 + 40 = 4560
Step 115: 4560 + 40 = 4600
Step 116: 4600 + 40 = 4640
Step 117: 4640 + 40 = 4680
Step 118: 4680 + 40 = 4720
Step 119: 4720 + 40 = 4760
Step 120: 4760 + 40 = 4800
Step 121: 4800 + 40 = 4840
Step 122: 4840 + 40 = 4880
Step 123: 4880 + 40 = 4920
Step 124: 4920 + 40 = 4960
Step 125: 4960 + 40 = 5000
Step 126: 5000 + 40 = 5040
Step 127: 5040 + 40 = 5080
Step 128: 5080 + 40 = 5120
Step 129: 5120 + 40 = 5160
Step 130: 5160 + 40 = 5200
Step 131: 5200 + 40 = 5240
Step 132: 5240 + 40 = 5280
Step 133: 5280 + 40 = 5320
Step 134: 5320 + 40 = 5360
Step 135: 5360 + 40 = 5400
Step 136: 5400 + 40 = 5440
Step 137: 5440 + 40 = 5480
Step 138: 5480 + 40 = 5520
Step 139: 5520 + 40 = 5560
Step 140: 5560 + 40 = 5600
Step 141: 5600 + 40 = 5640
Step 142: 5640 + 40 = 5680
Step 143: 5680 + 40 = 5720
Step 144: 5720 + 40 = 5760
Step 145: 5760 + 40 = 5800
Step 146: 5800 + 40 = 5840
Step 147: 5840 + 40 = 5880
Step 148: 5880 + 40 = 5920
Step 149: 5920 + 40 = 5960
Step 150: 5960 + 40 = 6000
Step 151: 6000 + 40 = 6040
Step 152: 6040 + 40 = 6080
Step 153: 6080 + 40 = 6120
Step 154: 6120 + 40 = 6160
Step 155: 6160 + 40 = 6200
Step 156: 6200 + 40 = 6240
Step 157: 6240 + 40 = 6280
Step 158: 6280 + 40 = 6320
Step 159: 6320 + 40 = 6360
Step 160: 6360 + 40 = 6400
Step 161: 6400 + 40 = 6440
Step 162: 6440 + 40 = 6480
Step 163: 6480 + 40 = 6520
Step 164: 6520 + 40 = 6560
Step 165: 6560 + 40 = 6600
Step 166: 6600 + 40 = 6640
Step 167: 6640 + 40 = 6680
Step 168: 6680 + 40 = 6720
Step 169: 6720 + 40 = 6760
Step 170: 6760 + 40 = 6800
Step 171: 6800 + 40 = 6840
Step 172: 6840 + 40 = 6880

So, 40*172 = 6880