OK, let's work through this together. We're starting with 115 and we're going to multiply it by 420, which means we add 115 to itself 420 times.
Step 1: 0 + 115 = 115
Step 2: 115 + 115 = 230
Step 3: 230 + 115 = 345
Step 4: 345 + 115 = 460
Step 5: 460 + 115 = 575
Step 6: 575 + 115 = 690
Step 7: 690 + 115 = 805
Step 8: 805 + 115 = 920
Step 9: 920 + 115 = 1035
Step 10: 1035 + 115 = 1150
Step 11: 1150 + 115 = 1265
Step 12: 1265 + 115 = 1380
Step 13: 1380 + 115 = 1495
Step 14: 1495 + 115 = 1610
Step 15: 1610 + 115 = 1725
Step 16: 1725 + 115 = 1840
Step 17: 1840 + 115 = 1955
Step 18: 1955 + 115 = 2070
Step 19: 2070 + 115 = 2185
Step 20: 2185 + 115 = 2300
Step 21: 2300 + 115 = 2415
Step 22: 2415 + 115 = 2530
Step 23: 2530 + 115 = 2645
Step 24: 2645 + 115 = 2760
Step 25: 2760 + 115 = 2875
Step 26: 2875 + 115 = 2990
Step 27: 2990 + 115 = 3105
Step 28: 3105 + 115 = 3220
Step 29: 3220 + 115 = 3335
Step 30: 3335 + 115 = 3450
Step 31: 3450 + 115 = 3565
Step 32: 3565 + 115 = 3680
Step 33: 3680 + 115 = 3795
Step 34: 3795 + 115 = 3910
Step 35: 3910 + 115 = 4025
Step 36: 4025 + 115 = 4140
Step 37: 4140 + 115 = 4255
Step 38: 4255 + 115 = 4370
Step 39: 4370 + 115 = 4485
Step 40: 4485 + 115 = 4600
Step 41: 4600 + 115 = 4715
Step 42: 4715 + 115 = 4830
Step 43: 4830 + 115 = 4945
Step 44: 4945 + 115 = 5060
Step 45: 5060 + 115 = 5175
Step 46: 5175 + 115 = 5290
Step 47: 5290 + 115 = 5405
Step 48: 5405 + 115 = 5520
Step 49: 5520 + 115 = 5635
Step 50: 5635 + 115 = 5750
Step 51: 5750 + 115 = 5865
Step 52: 5865 + 115 = 5980
Step 53: 5980 + 115 = 6095
Step 54: 6095 + 115 = 6210
Step 55: 6210 + 115 = 6325
Step 56: 6325 + 115 = 6440
Step 57: 6440 + 115 = 6555
Step 58: 6555 + 115 = 6670
Step 59: 6670 + 115 = 6785
Step 60: 6785 + 115 = 6900
Step 61: 6900 + 115 = 7015
Step 62: 7015 + 115 = 7130
Step 63: 7130 + 115 = 7245
Step 64: 7245 + 115 = 7360
Step 65: 7360 + 115 = 7475
Step 66: 7475 + 115 = 7590
Step 67: 7590 + 115 = 7705
Step 68: 7705 + 115 = 7820
Step 69: 7820 + 115 = 7935
Step 70: 7935 + 115 = 8050
Step 71: 8050 + 115 = 8165
Step 72: 8165 + 115 = 8280
Step 73: 8280 + 115 = 8395
Step 74: 8395 + 115 = 8510
Step 75: 8510 + 115 = 8625
Step 76: 8625 + 115 = 8740
Step 77: 8740 + 115 = 8855
Step 78: 8855 + 115 = 8970
Step 79: 8970 + 115 = 9085
Step 80: 9085 + 115 = 9200
Step 81: 9200 + 115 = 9315
Step 82: 9315 + 115 = 9430
Step 83: 9430 + 115 = 9545
Step 84: 9545 + 115 = 9660
Step 85: 9660 + 115 = 9775
Step 86: 9775 + 115 = 9890
Step 87: 9890 + 115 = 10005
Step 88: 10005 + 115 = 10120
Step 89: 10120 + 115 = 10235
Step 90: 10235 + 115 = 10350
Step 91: 10350 + 115 = 10465
Step 92: 10465 + 115 = 10580
Step 93: 10580 + 115 = 10695
Step 94: 10695 + 115 = 10810
Step 95: 10810 + 115 = 10925
Step 96: 10925 + 115 = 11040
Step 97: 11040 + 115 = 11155
Step 98: 11155 + 115 = 11270
Step 99: 11270 + 115 = 11385
Step 100: 11385 + 115 = 11500
Step 101: 11500 + 115 = 11615
Step 102: 11615 + 115 = 11730
Step 103: 11730 + 115 = 11845
Step 104: 11845 + 115 = 11960
Step 105: 11960 + 115 = 12075
Step 106: 12075 + 115 = 12190
Step 107: 12190 + 115 = 12305
Step 108: 12305 + 115 = 12420
Step 109: 12420 + 115 = 12535
Step 110: 12535 + 115 = 12650
Step 111: 12650 + 115 = 12765
Step 112: 12765 + 115 = 12880
Step 113: 12880 + 115 = 12995
Step 114: 12995 + 115 = 13110
Step 115: 13110 + 115 = 13225
Step 116: 13225 + 115 = 13340
Step 117: 13340 + 115 = 13455
Step 118: 13455 + 115 = 13570
Step 119: 13570 + 115 = 13685
Step 120: 13685 + 115 = 13800
Step 121: 13800 + 115 = 13915
Step 122: 13915 + 115 = 14030
Step 123: 14030 + 115 = 14145
Step 124: 14145 + 115 = 14260
Step 125: 14260 + 115 = 14375
Step 126: 14375 + 115 = 14490
Step 127: 14490 + 115 = 14605
Step 128: 14605 + 115 = 14720
Step 129: 14720 + 115 = 14835
Step 130: 14835 + 115 = 14950
Step 131: 14950 + 115 = 15065
Step 132: 15065 + 115 = 15180
Step 133: 15180 + 115 = 15295
Step 134: 15295 + 115 = 15410
Step 135: 15410 + 115 = 15525
Step 136: 15525 + 115 = 15640
Step 137: 15640 + 115 = 15755
Step 138: 15755 + 115 = 15870
Step 139: 15870 + 115 = 15985
Step 140: 15985 + 115 = 16100
Step 141: 16100 + 115 = 16215
Step 142: 16215 + 115 = 16330
Step 143: 16330 + 115 = 16445
Step 144: 16445 + 115 = 16560
Step 145: 16560 + 115 = 16675
Step 146: 16675 + 115 = 16790
Step 147: 16790 + 115 = 16905
Step 148: 16905 + 115 = 17020
Step 149: 17020 + 115 = 17135
Step 150: 17135 + 115 = 17250
Step 151: 17250 + 115 = 17365
Step 152: 17365 + 115 = 17480
Step 153: 17480 + 115 = 17595
Step 154: 17595 + 115 = 17710
Step 155: 17710 + 115 = 17825
Step 156: 17825 + 115 = 17940
Step 157: 17940 + 115 = 18055
Step 158: 18055 + 115 = 18170
Step 159: 18170 + 115 = 18285
Step 160: 18285 + 115 = 18400
Step 161: 18400 + 115 = 18515
Step 162: 18515 + 115 = 18630
Step 163: 18630 + 115 = 18745
Step 164: 18745 + 115 = 18860
Step 165: 18860 + 115 = 18975
Step 166: 18975 + 115 = 19090
Step 167: 19090 + 115 = 19205
Step 168: 19205 + 115 = 19320
Step 169: 19320 + 115 = 19435
Step 170: 19435 + 115 = 19550
Step 171: 19550 + 115 = 19665
Step 172: 19665 + 115 = 19780
Step 173: 19780 + 115 = 19895
Step 174: 19895 + 115 = 20010
Step 175: 20010 + 115 = 20125
Step 176: 20125 + 115 = 20240
Step 177: 20240 + 115 = 20355
Step 178: 20355 + 115 = 20470
Step 179: 20470 + 115 = 20585
Step 180: 20585 + 115 = 20700
Step 181: 20700 + 115 = 20815
Step 182: 20815 + 115 = 20930
Step 183: 20930 + 115 = 21045
Step 184: 21045 + 115 = 21160
Step 185: 21160 + 115 = 21275
Step 186: 21275 + 115 = 21390
Step 187: 21390 + 115 = 21505
Step 188: 21505 + 115 = 21620
Step 189: 21620 + 115 = 21735
Step 190: 21735 + 115 = 21850
Step 191: 21850 + 115 = 21965
Step 192: 21965 + 115 = 22080
Step 193: 22080 + 115 = 22195
Step 194: 22195 + 115 = 22310
Step 195: 22310 + 115 = 22425
Step 196: 22425 + 115 = 22540
Step 197: 22540 + 115 = 22655
Step 198: 22655 + 115 = 22770
Step 199: 22770 + 115 = 22885
Step 200: 22885 + 115 = 23000
Step 201: 23000 + 115 = 23115
Step 202: 23115 + 115 = 23230
Step 203: 23230 + 115 = 23345
Step 204: 23345 + 115 = 23460
Step 205: 23460 + 115 = 23575
Step 206: 23575 + 115 = 23690
Step 207: 23690 + 115 = 23805
Step 208: 23805 + 115 = 23920
Step 209: 23920 + 115 = 24035
Step 210: 24035 + 115 = 24150
Step 211: 24150 + 115 = 24265
Step 212: 24265 + 115 = 24380
Step 213: 24380 + 115 = 24495
Step 214: 24495 + 115 = 24610
Step 215: 24610 + 115 = 24725
Step 216: 24725 + 115 = 24840
Step 217: 24840 + 115 = 24955
Step 218: 24955 + 115 = 25070
Step 219: 25070 + 115 = 25185
Step 220: 25185 + 115 = 25300
Step 221: 25300 + 115 = 25415
Step 222: 25415 + 115 = 25530
Step 223: 25530 + 115 = 25645
Step 224: 25645 + 115 = 25760
Step 225: 25760 + 115 = 25875
Step 226: 25875 + 115 = 25990
Step 227: 25990 + 115 = 26105
Step 228: 26105 + 115 = 26220
Step 229: 26220 + 115 = 26335
Step 230: 26335 + 115 = 26450
Step 231: 26450 + 115 = 26565
Step 232: 26565 + 115 = 26680
Step 233: 26680 + 115 = 26795
Step 234: 26795 + 115 = 26910
Step 235: 26910 + 115 = 27025
Step 236: 27025 + 115 = 27140
Step 237: 27140 + 115 = 27255
Step 238: 27255 + 115 = 27370
Step 239: 27370 + 115 = 27485
Step 240: 27485 + 115 = 27600
Step 241: 27600 + 115 = 27715
Step 242: 27715 + 115 = 27830
Step 243: 27830 + 115 = 27945
Step 244: 27945 + 115 = 28060
Step 245: 28060 + 115 = 28175
Step 246: 28175 + 115 = 28290
Step 247: 28290 + 115 = 28405
Step 248: 28405 + 115 = 28520
Step 249: 28520 + 115 = 28635
Step 250: 28635 + 115 = 28750
Step 251: 28750 + 115 = 28865
Step 252: 28865 + 115 = 28980
Step 253: 28980 + 115 = 29095
Step 254: 29095 + 115 = 29210
Step 255: 29210 + 115 = 29325
Step 256: 29325 + 115 = 29440
Step 257: 29440 + 115 = 29555
Step 258: 29555 + 115 = 29670
Step 259: 29670 + 115 = 29785
Step 260: 29785 + 115 = 29900
Step 261: 29900 + 115 = 30015
Step 262: 30015 + 115 = 30130
Step 263: 30130 + 115 = 30245
Step 264: 30245 + 115 = 30360
Step 265: 30360 + 115 = 30475
Step 266: 30475 + 115 = 30590
Step 267: 30590 + 115 = 30705
Step 268: 30705 + 115 = 30820
Step 269: 30820 + 115 = 30935
Step 270: 30935 + 115 = 31050
Step 271: 31050 + 115 = 31165
Step 272: 31165 + 115 = 31280
Step 273: 31280 + 115 = 31395
Step 274: 31395 + 115 = 31510
Step 275: 31510 + 115 = 31625
Step 276: 31625 + 115 = 31740
Step 277: 31740 + 115 = 31855
Step 278: 31855 + 115 = 31970
Step 279: 31970 + 115 = 32085
Step 280: 32085 + 115 = 32200
Step 281: 32200 + 115 = 32315
Step 282: 32315 + 115 = 32430
Step 283: 32430 + 115 = 32545
Step 284: 32545 + 115 = 32660
Step 285: 32660 + 115 = 32775
Step 286: 32775 + 115 = 32890
Step 287: 32890 + 115 = 33005
Step 288: 33005 + 115 = 33120
Step 289: 33120 + 115 = 33235
Step 290: 33235 + 115 = 33350
Step 291: 33350 + 115 = 33465
Step 292: 33465 + 115 = 33580
Step 293: 33580 + 115 = 33695
Step 294: 33695 + 115 = 33810
Step 295: 33810 + 115 = 33925
Step 296: 33925 + 115 = 34040
Step 297: 34040 + 115 = 34155
Step 298: 34155 + 115 = 34270
Step 299: 34270 + 115 = 34385
Step 300: 34385 + 115 = 34500
Step 301: 34500 + 115 = 34615
Step 302: 34615 + 115 = 34730
Step 303: 34730 + 115 = 34845
Step 304: 34845 + 115 = 34960
Step 305: 34960 + 115 = 35075
Step 306: 35075 + 115 = 35190
Step 307: 35190 + 115 = 35305
Step 308: 35305 + 115 = 35420
Step 309: 35420 + 115 = 35535
Step 310: 35535 + 115 = 35650
Step 311: 35650 + 115 = 35765
Step 312: 35765 + 115 = 35880
Step 313: 35880 + 115 = 35995
Step 314: 35995 + 115 = 36110
Step 315: 36110 + 115 = 36225
Step 316: 36225 + 115 = 36340
Step 317: 36340 + 115 = 36455
Step 318: 36455 + 115 = 36570
Step 319: 36570 + 115 = 36685
Step 320: 36685 + 115 = 36800
Step 321: 36800 + 115 = 36915
Step 322: 36915 + 115 = 37030
Step 323: 37030 + 115 = 37145
Step 324: 37145 + 115 = 37260
Step 325: 37260 + 115 = 37375
Step 326: 37375 + 115 = 37490
Step 327: 37490 + 115 = 37605
Step 328: 37605 + 115 = 37720
Step 329: 37720 + 115 = 37835
Step 330: 37835 + 115 = 37950
Step 331: 37950 + 115 = 38065
Step 332: 38065 + 115 = 38180
Step 333: 38180 + 115 = 38295
Step 334: 38295 + 115 = 38410
Step 335: 38410 + 115 = 38525
Step 336: 38525 + 115 = 38640
Step 337: 38640 + 115 = 38755
Step 338: 38755 + 115 = 38870
Step 339: 38870 + 115 = 38985
Step 340: 38985 + 115 = 39100
Step 341: 39100 + 115 = 39215
Step 342: 39215 + 115 = 39330
Step 343: 39330 + 115 = 39445
Step 344: 39445 + 115 = 39560
Step 345: 39560 + 115 = 39675
Step 346: 39675 + 115 = 39790
Step 347: 39790 + 115 = 39905
Step 348: 39905 + 115 = 40020
Step 349: 40020 + 115 = 40135
Step 350: 40135 + 115 = 40250
Step 351: 40250 + 115 = 40365
Step 352: 40365 + 115 = 40480
Step 353: 40480 + 115 = 40595
Step 354: 40595 + 115 = 40710
Step 355: 40710 + 115 = 40825
Step 356: 40825 + 115 = 40940
Step 357: 40940 + 115 = 41055
Step 358: 41055 + 115 = 41170
Step 359: 41170 + 115 = 41285
Step 360: 41285 + 115 = 41400
Step 361: 41400 + 115 = 41515
Step 362: 41515 + 115 = 41630
Step 363: 41630 + 115 = 41745
Step 364: 41745 + 115 = 41860
Step 365: 41860 + 115 = 41975
Step 366: 41975 + 115 = 42090
Step 367: 42090 + 115 = 42205
Step 368: 42205 + 115 = 42320
Step 369: 42320 + 115 = 42435
Step 370: 42435 + 115 = 42550
Step 371: 42550 + 115 = 42665
Step 372: 42665 + 115 = 42780
Step 373: 42780 + 115 = 42895
Step 374: 42895 + 115 = 43010
Step 375: 43010 + 115 = 43125
Step 376: 43125 + 115 = 43240
Step 377: 43240 + 115 = 43355
Step 378: 43355 + 115 = 43470
Step 379: 43470 + 115 = 43585
Step 380: 43585 + 115 = 43700
Step 381: 43700 + 115 = 43815
Step 382: 43815 + 115 = 43930
Step 383: 43930 + 115 = 44045
Step 384: 44045 + 115 = 44160
Step 385: 44160 + 115 = 44275
Step 386: 44275 + 115 = 44390
Step 387: 44390 + 115 = 44505
Step 388: 44505 + 115 = 44620
Step 389: 44620 + 115 = 44735
Step 390: 44735 + 115 = 44850
Step 391: 44850 + 115 = 44965
Step 392: 44965 + 115 = 45080
Step 393: 45080 + 115 = 45195
Step 394: 45195 + 115 = 45310
Step 395: 45310 + 115 = 45425
Step 396: 45425 + 115 = 45540
Step 397: 45540 + 115 = 45655
Step 398: 45655 + 115 = 45770
Step 399: 45770 + 115 = 45885
Step 400: 45885 + 115 = 46000
Step 401: 46000 + 115 = 46115
Step 402: 46115 + 115 = 46230
Step 403: 46230 + 115 = 46345
Step 404: 46345 + 115 = 46460
Step 405: 46460 + 115 = 46575
Step 406: 46575 + 115 = 46690
Step 407: 46690 + 115 = 46805
Step 408: 46805 + 115 = 46920
Step 409: 46920 + 115 = 47035
Step 410: 47035 + 115 = 47150
Step 411: 47150 + 115 = 47265
Step 412: 47265 + 115 = 47380
Step 413: 47380 + 115 = 47495
Step 414: 47495 + 115 = 47610
Step 415: 47610 + 115 = 47725
Step 416: 47725 + 115 = 47840
Step 417: 47840 + 115 = 47955
Step 418: 47955 + 115 = 48070
Step 419: 48070 + 115 = 48185
Step 420: 48185 + 115 = 48300

So, 115*420 = 48300