OK, let's crack this. We're given 961 and our task is to multiply it by 420. Essentially, we'll be adding 961 to itself 420 times.
Step 1: 0 + 961 = 961
Step 2: 961 + 961 = 1922
Step 3: 1922 + 961 = 2883
Step 4: 2883 + 961 = 3844
Step 5: 3844 + 961 = 4805
Step 6: 4805 + 961 = 5766
Step 7: 5766 + 961 = 6727
Step 8: 6727 + 961 = 7688
Step 9: 7688 + 961 = 8649
Step 10: 8649 + 961 = 9610
Step 11: 9610 + 961 = 10571
Step 12: 10571 + 961 = 11532
Step 13: 11532 + 961 = 12493
Step 14: 12493 + 961 = 13454
Step 15: 13454 + 961 = 14415
Step 16: 14415 + 961 = 15376
Step 17: 15376 + 961 = 16337
Step 18: 16337 + 961 = 17298
Step 19: 17298 + 961 = 18259
Step 20: 18259 + 961 = 19220
Step 21: 19220 + 961 = 20181
Step 22: 20181 + 961 = 21142
Step 23: 21142 + 961 = 22103
Step 24: 22103 + 961 = 23064
Step 25: 23064 + 961 = 24025
Step 26: 24025 + 961 = 24986
Step 27: 24986 + 961 = 25947
Step 28: 25947 + 961 = 26908
Step 29: 26908 + 961 = 27869
Step 30: 27869 + 961 = 28830
Step 31: 28830 + 961 = 29791
Step 32: 29791 + 961 = 30752
Step 33: 30752 + 961 = 31713
Step 34: 31713 + 961 = 32674
Step 35: 32674 + 961 = 33635
Step 36: 33635 + 961 = 34596
Step 37: 34596 + 961 = 35557
Step 38: 35557 + 961 = 36518
Step 39: 36518 + 961 = 37479
Step 40: 37479 + 961 = 38440
Step 41: 38440 + 961 = 39401
Step 42: 39401 + 961 = 40362
Step 43: 40362 + 961 = 41323
Step 44: 41323 + 961 = 42284
Step 45: 42284 + 961 = 43245
Step 46: 43245 + 961 = 44206
Step 47: 44206 + 961 = 45167
Step 48: 45167 + 961 = 46128
Step 49: 46128 + 961 = 47089
Step 50: 47089 + 961 = 48050
Step 51: 48050 + 961 = 49011
Step 52: 49011 + 961 = 49972
Step 53: 49972 + 961 = 50933
Step 54: 50933 + 961 = 51894
Step 55: 51894 + 961 = 52855
Step 56: 52855 + 961 = 53816
Step 57: 53816 + 961 = 54777
Step 58: 54777 + 961 = 55738
Step 59: 55738 + 961 = 56699
Step 60: 56699 + 961 = 57660
Step 61: 57660 + 961 = 58621
Step 62: 58621 + 961 = 59582
Step 63: 59582 + 961 = 60543
Step 64: 60543 + 961 = 61504
Step 65: 61504 + 961 = 62465
Step 66: 62465 + 961 = 63426
Step 67: 63426 + 961 = 64387
Step 68: 64387 + 961 = 65348
Step 69: 65348 + 961 = 66309
Step 70: 66309 + 961 = 67270
Step 71: 67270 + 961 = 68231
Step 72: 68231 + 961 = 69192
Step 73: 69192 + 961 = 70153
Step 74: 70153 + 961 = 71114
Step 75: 71114 + 961 = 72075
Step 76: 72075 + 961 = 73036
Step 77: 73036 + 961 = 73997
Step 78: 73997 + 961 = 74958
Step 79: 74958 + 961 = 75919
Step 80: 75919 + 961 = 76880
Step 81: 76880 + 961 = 77841
Step 82: 77841 + 961 = 78802
Step 83: 78802 + 961 = 79763
Step 84: 79763 + 961 = 80724
Step 85: 80724 + 961 = 81685
Step 86: 81685 + 961 = 82646
Step 87: 82646 + 961 = 83607
Step 88: 83607 + 961 = 84568
Step 89: 84568 + 961 = 85529
Step 90: 85529 + 961 = 86490
Step 91: 86490 + 961 = 87451
Step 92: 87451 + 961 = 88412
Step 93: 88412 + 961 = 89373
Step 94: 89373 + 961 = 90334
Step 95: 90334 + 961 = 91295
Step 96: 91295 + 961 = 92256
Step 97: 92256 + 961 = 93217
Step 98: 93217 + 961 = 94178
Step 99: 94178 + 961 = 95139
Step 100: 95139 + 961 = 96100
Step 101: 96100 + 961 = 97061
Step 102: 97061 + 961 = 98022
Step 103: 98022 + 961 = 98983
Step 104: 98983 + 961 = 99944
Step 105: 99944 + 961 = 100905
Step 106: 100905 + 961 = 101866
Step 107: 101866 + 961 = 102827
Step 108: 102827 + 961 = 103788
Step 109: 103788 + 961 = 104749
Step 110: 104749 + 961 = 105710
Step 111: 105710 + 961 = 106671
Step 112: 106671 + 961 = 107632
Step 113: 107632 + 961 = 108593
Step 114: 108593 + 961 = 109554
Step 115: 109554 + 961 = 110515
Step 116: 110515 + 961 = 111476
Step 117: 111476 + 961 = 112437
Step 118: 112437 + 961 = 113398
Step 119: 113398 + 961 = 114359
Step 120: 114359 + 961 = 115320
Step 121: 115320 + 961 = 116281
Step 122: 116281 + 961 = 117242
Step 123: 117242 + 961 = 118203
Step 124: 118203 + 961 = 119164
Step 125: 119164 + 961 = 120125
Step 126: 120125 + 961 = 121086
Step 127: 121086 + 961 = 122047
Step 128: 122047 + 961 = 123008
Step 129: 123008 + 961 = 123969
Step 130: 123969 + 961 = 124930
Step 131: 124930 + 961 = 125891
Step 132: 125891 + 961 = 126852
Step 133: 126852 + 961 = 127813
Step 134: 127813 + 961 = 128774
Step 135: 128774 + 961 = 129735
Step 136: 129735 + 961 = 130696
Step 137: 130696 + 961 = 131657
Step 138: 131657 + 961 = 132618
Step 139: 132618 + 961 = 133579
Step 140: 133579 + 961 = 134540
Step 141: 134540 + 961 = 135501
Step 142: 135501 + 961 = 136462
Step 143: 136462 + 961 = 137423
Step 144: 137423 + 961 = 138384
Step 145: 138384 + 961 = 139345
Step 146: 139345 + 961 = 140306
Step 147: 140306 + 961 = 141267
Step 148: 141267 + 961 = 142228
Step 149: 142228 + 961 = 143189
Step 150: 143189 + 961 = 144150
Step 151: 144150 + 961 = 145111
Step 152: 145111 + 961 = 146072
Step 153: 146072 + 961 = 147033
Step 154: 147033 + 961 = 147994
Step 155: 147994 + 961 = 148955
Step 156: 148955 + 961 = 149916
Step 157: 149916 + 961 = 150877
Step 158: 150877 + 961 = 151838
Step 159: 151838 + 961 = 152799
Step 160: 152799 + 961 = 153760
Step 161: 153760 + 961 = 154721
Step 162: 154721 + 961 = 155682
Step 163: 155682 + 961 = 156643
Step 164: 156643 + 961 = 157604
Step 165: 157604 + 961 = 158565
Step 166: 158565 + 961 = 159526
Step 167: 159526 + 961 = 160487
Step 168: 160487 + 961 = 161448
Step 169: 161448 + 961 = 162409
Step 170: 162409 + 961 = 163370
Step 171: 163370 + 961 = 164331
Step 172: 164331 + 961 = 165292
Step 173: 165292 + 961 = 166253
Step 174: 166253 + 961 = 167214
Step 175: 167214 + 961 = 168175
Step 176: 168175 + 961 = 169136
Step 177: 169136 + 961 = 170097
Step 178: 170097 + 961 = 171058
Step 179: 171058 + 961 = 172019
Step 180: 172019 + 961 = 172980
Step 181: 172980 + 961 = 173941
Step 182: 173941 + 961 = 174902
Step 183: 174902 + 961 = 175863
Step 184: 175863 + 961 = 176824
Step 185: 176824 + 961 = 177785
Step 186: 177785 + 961 = 178746
Step 187: 178746 + 961 = 179707
Step 188: 179707 + 961 = 180668
Step 189: 180668 + 961 = 181629
Step 190: 181629 + 961 = 182590
Step 191: 182590 + 961 = 183551
Step 192: 183551 + 961 = 184512
Step 193: 184512 + 961 = 185473
Step 194: 185473 + 961 = 186434
Step 195: 186434 + 961 = 187395
Step 196: 187395 + 961 = 188356
Step 197: 188356 + 961 = 189317
Step 198: 189317 + 961 = 190278
Step 199: 190278 + 961 = 191239
Step 200: 191239 + 961 = 192200
Step 201: 192200 + 961 = 193161
Step 202: 193161 + 961 = 194122
Step 203: 194122 + 961 = 195083
Step 204: 195083 + 961 = 196044
Step 205: 196044 + 961 = 197005
Step 206: 197005 + 961 = 197966
Step 207: 197966 + 961 = 198927
Step 208: 198927 + 961 = 199888
Step 209: 199888 + 961 = 200849
Step 210: 200849 + 961 = 201810
Step 211: 201810 + 961 = 202771
Step 212: 202771 + 961 = 203732
Step 213: 203732 + 961 = 204693
Step 214: 204693 + 961 = 205654
Step 215: 205654 + 961 = 206615
Step 216: 206615 + 961 = 207576
Step 217: 207576 + 961 = 208537
Step 218: 208537 + 961 = 209498
Step 219: 209498 + 961 = 210459
Step 220: 210459 + 961 = 211420
Step 221: 211420 + 961 = 212381
Step 222: 212381 + 961 = 213342
Step 223: 213342 + 961 = 214303
Step 224: 214303 + 961 = 215264
Step 225: 215264 + 961 = 216225
Step 226: 216225 + 961 = 217186
Step 227: 217186 + 961 = 218147
Step 228: 218147 + 961 = 219108
Step 229: 219108 + 961 = 220069
Step 230: 220069 + 961 = 221030
Step 231: 221030 + 961 = 221991
Step 232: 221991 + 961 = 222952
Step 233: 222952 + 961 = 223913
Step 234: 223913 + 961 = 224874
Step 235: 224874 + 961 = 225835
Step 236: 225835 + 961 = 226796
Step 237: 226796 + 961 = 227757
Step 238: 227757 + 961 = 228718
Step 239: 228718 + 961 = 229679
Step 240: 229679 + 961 = 230640
Step 241: 230640 + 961 = 231601
Step 242: 231601 + 961 = 232562
Step 243: 232562 + 961 = 233523
Step 244: 233523 + 961 = 234484
Step 245: 234484 + 961 = 235445
Step 246: 235445 + 961 = 236406
Step 247: 236406 + 961 = 237367
Step 248: 237367 + 961 = 238328
Step 249: 238328 + 961 = 239289
Step 250: 239289 + 961 = 240250
Step 251: 240250 + 961 = 241211
Step 252: 241211 + 961 = 242172
Step 253: 242172 + 961 = 243133
Step 254: 243133 + 961 = 244094
Step 255: 244094 + 961 = 245055
Step 256: 245055 + 961 = 246016
Step 257: 246016 + 961 = 246977
Step 258: 246977 + 961 = 247938
Step 259: 247938 + 961 = 248899
Step 260: 248899 + 961 = 249860
Step 261: 249860 + 961 = 250821
Step 262: 250821 + 961 = 251782
Step 263: 251782 + 961 = 252743
Step 264: 252743 + 961 = 253704
Step 265: 253704 + 961 = 254665
Step 266: 254665 + 961 = 255626
Step 267: 255626 + 961 = 256587
Step 268: 256587 + 961 = 257548
Step 269: 257548 + 961 = 258509
Step 270: 258509 + 961 = 259470
Step 271: 259470 + 961 = 260431
Step 272: 260431 + 961 = 261392
Step 273: 261392 + 961 = 262353
Step 274: 262353 + 961 = 263314
Step 275: 263314 + 961 = 264275
Step 276: 264275 + 961 = 265236
Step 277: 265236 + 961 = 266197
Step 278: 266197 + 961 = 267158
Step 279: 267158 + 961 = 268119
Step 280: 268119 + 961 = 269080
Step 281: 269080 + 961 = 270041
Step 282: 270041 + 961 = 271002
Step 283: 271002 + 961 = 271963
Step 284: 271963 + 961 = 272924
Step 285: 272924 + 961 = 273885
Step 286: 273885 + 961 = 274846
Step 287: 274846 + 961 = 275807
Step 288: 275807 + 961 = 276768
Step 289: 276768 + 961 = 277729
Step 290: 277729 + 961 = 278690
Step 291: 278690 + 961 = 279651
Step 292: 279651 + 961 = 280612
Step 293: 280612 + 961 = 281573
Step 294: 281573 + 961 = 282534
Step 295: 282534 + 961 = 283495
Step 296: 283495 + 961 = 284456
Step 297: 284456 + 961 = 285417
Step 298: 285417 + 961 = 286378
Step 299: 286378 + 961 = 287339
Step 300: 287339 + 961 = 288300
Step 301: 288300 + 961 = 289261
Step 302: 289261 + 961 = 290222
Step 303: 290222 + 961 = 291183
Step 304: 291183 + 961 = 292144
Step 305: 292144 + 961 = 293105
Step 306: 293105 + 961 = 294066
Step 307: 294066 + 961 = 295027
Step 308: 295027 + 961 = 295988
Step 309: 295988 + 961 = 296949
Step 310: 296949 + 961 = 297910
Step 311: 297910 + 961 = 298871
Step 312: 298871 + 961 = 299832
Step 313: 299832 + 961 = 300793
Step 314: 300793 + 961 = 301754
Step 315: 301754 + 961 = 302715
Step 316: 302715 + 961 = 303676
Step 317: 303676 + 961 = 304637
Step 318: 304637 + 961 = 305598
Step 319: 305598 + 961 = 306559
Step 320: 306559 + 961 = 307520
Step 321: 307520 + 961 = 308481
Step 322: 308481 + 961 = 309442
Step 323: 309442 + 961 = 310403
Step 324: 310403 + 961 = 311364
Step 325: 311364 + 961 = 312325
Step 326: 312325 + 961 = 313286
Step 327: 313286 + 961 = 314247
Step 328: 314247 + 961 = 315208
Step 329: 315208 + 961 = 316169
Step 330: 316169 + 961 = 317130
Step 331: 317130 + 961 = 318091
Step 332: 318091 + 961 = 319052
Step 333: 319052 + 961 = 320013
Step 334: 320013 + 961 = 320974
Step 335: 320974 + 961 = 321935
Step 336: 321935 + 961 = 322896
Step 337: 322896 + 961 = 323857
Step 338: 323857 + 961 = 324818
Step 339: 324818 + 961 = 325779
Step 340: 325779 + 961 = 326740
Step 341: 326740 + 961 = 327701
Step 342: 327701 + 961 = 328662
Step 343: 328662 + 961 = 329623
Step 344: 329623 + 961 = 330584
Step 345: 330584 + 961 = 331545
Step 346: 331545 + 961 = 332506
Step 347: 332506 + 961 = 333467
Step 348: 333467 + 961 = 334428
Step 349: 334428 + 961 = 335389
Step 350: 335389 + 961 = 336350
Step 351: 336350 + 961 = 337311
Step 352: 337311 + 961 = 338272
Step 353: 338272 + 961 = 339233
Step 354: 339233 + 961 = 340194
Step 355: 340194 + 961 = 341155
Step 356: 341155 + 961 = 342116
Step 357: 342116 + 961 = 343077
Step 358: 343077 + 961 = 344038
Step 359: 344038 + 961 = 344999
Step 360: 344999 + 961 = 345960
Step 361: 345960 + 961 = 346921
Step 362: 346921 + 961 = 347882
Step 363: 347882 + 961 = 348843
Step 364: 348843 + 961 = 349804
Step 365: 349804 + 961 = 350765
Step 366: 350765 + 961 = 351726
Step 367: 351726 + 961 = 352687
Step 368: 352687 + 961 = 353648
Step 369: 353648 + 961 = 354609
Step 370: 354609 + 961 = 355570
Step 371: 355570 + 961 = 356531
Step 372: 356531 + 961 = 357492
Step 373: 357492 + 961 = 358453
Step 374: 358453 + 961 = 359414
Step 375: 359414 + 961 = 360375
Step 376: 360375 + 961 = 361336
Step 377: 361336 + 961 = 362297
Step 378: 362297 + 961 = 363258
Step 379: 363258 + 961 = 364219
Step 380: 364219 + 961 = 365180
Step 381: 365180 + 961 = 366141
Step 382: 366141 + 961 = 367102
Step 383: 367102 + 961 = 368063
Step 384: 368063 + 961 = 369024
Step 385: 369024 + 961 = 369985
Step 386: 369985 + 961 = 370946
Step 387: 370946 + 961 = 371907
Step 388: 371907 + 961 = 372868
Step 389: 372868 + 961 = 373829
Step 390: 373829 + 961 = 374790
Step 391: 374790 + 961 = 375751
Step 392: 375751 + 961 = 376712
Step 393: 376712 + 961 = 377673
Step 394: 377673 + 961 = 378634
Step 395: 378634 + 961 = 379595
Step 396: 379595 + 961 = 380556
Step 397: 380556 + 961 = 381517
Step 398: 381517 + 961 = 382478
Step 399: 382478 + 961 = 383439
Step 400: 383439 + 961 = 384400
Step 401: 384400 + 961 = 385361
Step 402: 385361 + 961 = 386322
Step 403: 386322 + 961 = 387283
Step 404: 387283 + 961 = 388244
Step 405: 388244 + 961 = 389205
Step 406: 389205 + 961 = 390166
Step 407: 390166 + 961 = 391127
Step 408: 391127 + 961 = 392088
Step 409: 392088 + 961 = 393049
Step 410: 393049 + 961 = 394010
Step 411: 394010 + 961 = 394971
Step 412: 394971 + 961 = 395932
Step 413: 395932 + 961 = 396893
Step 414: 396893 + 961 = 397854
Step 415: 397854 + 961 = 398815
Step 416: 398815 + 961 = 399776
Step 417: 399776 + 961 = 400737
Step 418: 400737 + 961 = 401698
Step 419: 401698 + 961 = 402659
Step 420: 402659 + 961 = 403620

So, 961*420 = 403620