Let's roll up our sleeves and solve this. We have 646 and we're going to multiply it by 415, essentially adding 646 to itself 415 times.
Step 1: 0 + 646 = 646
Step 2: 646 + 646 = 1292
Step 3: 1292 + 646 = 1938
Step 4: 1938 + 646 = 2584
Step 5: 2584 + 646 = 3230
Step 6: 3230 + 646 = 3876
Step 7: 3876 + 646 = 4522
Step 8: 4522 + 646 = 5168
Step 9: 5168 + 646 = 5814
Step 10: 5814 + 646 = 6460
Step 11: 6460 + 646 = 7106
Step 12: 7106 + 646 = 7752
Step 13: 7752 + 646 = 8398
Step 14: 8398 + 646 = 9044
Step 15: 9044 + 646 = 9690
Step 16: 9690 + 646 = 10336
Step 17: 10336 + 646 = 10982
Step 18: 10982 + 646 = 11628
Step 19: 11628 + 646 = 12274
Step 20: 12274 + 646 = 12920
Step 21: 12920 + 646 = 13566
Step 22: 13566 + 646 = 14212
Step 23: 14212 + 646 = 14858
Step 24: 14858 + 646 = 15504
Step 25: 15504 + 646 = 16150
Step 26: 16150 + 646 = 16796
Step 27: 16796 + 646 = 17442
Step 28: 17442 + 646 = 18088
Step 29: 18088 + 646 = 18734
Step 30: 18734 + 646 = 19380
Step 31: 19380 + 646 = 20026
Step 32: 20026 + 646 = 20672
Step 33: 20672 + 646 = 21318
Step 34: 21318 + 646 = 21964
Step 35: 21964 + 646 = 22610
Step 36: 22610 + 646 = 23256
Step 37: 23256 + 646 = 23902
Step 38: 23902 + 646 = 24548
Step 39: 24548 + 646 = 25194
Step 40: 25194 + 646 = 25840
Step 41: 25840 + 646 = 26486
Step 42: 26486 + 646 = 27132
Step 43: 27132 + 646 = 27778
Step 44: 27778 + 646 = 28424
Step 45: 28424 + 646 = 29070
Step 46: 29070 + 646 = 29716
Step 47: 29716 + 646 = 30362
Step 48: 30362 + 646 = 31008
Step 49: 31008 + 646 = 31654
Step 50: 31654 + 646 = 32300
Step 51: 32300 + 646 = 32946
Step 52: 32946 + 646 = 33592
Step 53: 33592 + 646 = 34238
Step 54: 34238 + 646 = 34884
Step 55: 34884 + 646 = 35530
Step 56: 35530 + 646 = 36176
Step 57: 36176 + 646 = 36822
Step 58: 36822 + 646 = 37468
Step 59: 37468 + 646 = 38114
Step 60: 38114 + 646 = 38760
Step 61: 38760 + 646 = 39406
Step 62: 39406 + 646 = 40052
Step 63: 40052 + 646 = 40698
Step 64: 40698 + 646 = 41344
Step 65: 41344 + 646 = 41990
Step 66: 41990 + 646 = 42636
Step 67: 42636 + 646 = 43282
Step 68: 43282 + 646 = 43928
Step 69: 43928 + 646 = 44574
Step 70: 44574 + 646 = 45220
Step 71: 45220 + 646 = 45866
Step 72: 45866 + 646 = 46512
Step 73: 46512 + 646 = 47158
Step 74: 47158 + 646 = 47804
Step 75: 47804 + 646 = 48450
Step 76: 48450 + 646 = 49096
Step 77: 49096 + 646 = 49742
Step 78: 49742 + 646 = 50388
Step 79: 50388 + 646 = 51034
Step 80: 51034 + 646 = 51680
Step 81: 51680 + 646 = 52326
Step 82: 52326 + 646 = 52972
Step 83: 52972 + 646 = 53618
Step 84: 53618 + 646 = 54264
Step 85: 54264 + 646 = 54910
Step 86: 54910 + 646 = 55556
Step 87: 55556 + 646 = 56202
Step 88: 56202 + 646 = 56848
Step 89: 56848 + 646 = 57494
Step 90: 57494 + 646 = 58140
Step 91: 58140 + 646 = 58786
Step 92: 58786 + 646 = 59432
Step 93: 59432 + 646 = 60078
Step 94: 60078 + 646 = 60724
Step 95: 60724 + 646 = 61370
Step 96: 61370 + 646 = 62016
Step 97: 62016 + 646 = 62662
Step 98: 62662 + 646 = 63308
Step 99: 63308 + 646 = 63954
Step 100: 63954 + 646 = 64600
Step 101: 64600 + 646 = 65246
Step 102: 65246 + 646 = 65892
Step 103: 65892 + 646 = 66538
Step 104: 66538 + 646 = 67184
Step 105: 67184 + 646 = 67830
Step 106: 67830 + 646 = 68476
Step 107: 68476 + 646 = 69122
Step 108: 69122 + 646 = 69768
Step 109: 69768 + 646 = 70414
Step 110: 70414 + 646 = 71060
Step 111: 71060 + 646 = 71706
Step 112: 71706 + 646 = 72352
Step 113: 72352 + 646 = 72998
Step 114: 72998 + 646 = 73644
Step 115: 73644 + 646 = 74290
Step 116: 74290 + 646 = 74936
Step 117: 74936 + 646 = 75582
Step 118: 75582 + 646 = 76228
Step 119: 76228 + 646 = 76874
Step 120: 76874 + 646 = 77520
Step 121: 77520 + 646 = 78166
Step 122: 78166 + 646 = 78812
Step 123: 78812 + 646 = 79458
Step 124: 79458 + 646 = 80104
Step 125: 80104 + 646 = 80750
Step 126: 80750 + 646 = 81396
Step 127: 81396 + 646 = 82042
Step 128: 82042 + 646 = 82688
Step 129: 82688 + 646 = 83334
Step 130: 83334 + 646 = 83980
Step 131: 83980 + 646 = 84626
Step 132: 84626 + 646 = 85272
Step 133: 85272 + 646 = 85918
Step 134: 85918 + 646 = 86564
Step 135: 86564 + 646 = 87210
Step 136: 87210 + 646 = 87856
Step 137: 87856 + 646 = 88502
Step 138: 88502 + 646 = 89148
Step 139: 89148 + 646 = 89794
Step 140: 89794 + 646 = 90440
Step 141: 90440 + 646 = 91086
Step 142: 91086 + 646 = 91732
Step 143: 91732 + 646 = 92378
Step 144: 92378 + 646 = 93024
Step 145: 93024 + 646 = 93670
Step 146: 93670 + 646 = 94316
Step 147: 94316 + 646 = 94962
Step 148: 94962 + 646 = 95608
Step 149: 95608 + 646 = 96254
Step 150: 96254 + 646 = 96900
Step 151: 96900 + 646 = 97546
Step 152: 97546 + 646 = 98192
Step 153: 98192 + 646 = 98838
Step 154: 98838 + 646 = 99484
Step 155: 99484 + 646 = 100130
Step 156: 100130 + 646 = 100776
Step 157: 100776 + 646 = 101422
Step 158: 101422 + 646 = 102068
Step 159: 102068 + 646 = 102714
Step 160: 102714 + 646 = 103360
Step 161: 103360 + 646 = 104006
Step 162: 104006 + 646 = 104652
Step 163: 104652 + 646 = 105298
Step 164: 105298 + 646 = 105944
Step 165: 105944 + 646 = 106590
Step 166: 106590 + 646 = 107236
Step 167: 107236 + 646 = 107882
Step 168: 107882 + 646 = 108528
Step 169: 108528 + 646 = 109174
Step 170: 109174 + 646 = 109820
Step 171: 109820 + 646 = 110466
Step 172: 110466 + 646 = 111112
Step 173: 111112 + 646 = 111758
Step 174: 111758 + 646 = 112404
Step 175: 112404 + 646 = 113050
Step 176: 113050 + 646 = 113696
Step 177: 113696 + 646 = 114342
Step 178: 114342 + 646 = 114988
Step 179: 114988 + 646 = 115634
Step 180: 115634 + 646 = 116280
Step 181: 116280 + 646 = 116926
Step 182: 116926 + 646 = 117572
Step 183: 117572 + 646 = 118218
Step 184: 118218 + 646 = 118864
Step 185: 118864 + 646 = 119510
Step 186: 119510 + 646 = 120156
Step 187: 120156 + 646 = 120802
Step 188: 120802 + 646 = 121448
Step 189: 121448 + 646 = 122094
Step 190: 122094 + 646 = 122740
Step 191: 122740 + 646 = 123386
Step 192: 123386 + 646 = 124032
Step 193: 124032 + 646 = 124678
Step 194: 124678 + 646 = 125324
Step 195: 125324 + 646 = 125970
Step 196: 125970 + 646 = 126616
Step 197: 126616 + 646 = 127262
Step 198: 127262 + 646 = 127908
Step 199: 127908 + 646 = 128554
Step 200: 128554 + 646 = 129200
Step 201: 129200 + 646 = 129846
Step 202: 129846 + 646 = 130492
Step 203: 130492 + 646 = 131138
Step 204: 131138 + 646 = 131784
Step 205: 131784 + 646 = 132430
Step 206: 132430 + 646 = 133076
Step 207: 133076 + 646 = 133722
Step 208: 133722 + 646 = 134368
Step 209: 134368 + 646 = 135014
Step 210: 135014 + 646 = 135660
Step 211: 135660 + 646 = 136306
Step 212: 136306 + 646 = 136952
Step 213: 136952 + 646 = 137598
Step 214: 137598 + 646 = 138244
Step 215: 138244 + 646 = 138890
Step 216: 138890 + 646 = 139536
Step 217: 139536 + 646 = 140182
Step 218: 140182 + 646 = 140828
Step 219: 140828 + 646 = 141474
Step 220: 141474 + 646 = 142120
Step 221: 142120 + 646 = 142766
Step 222: 142766 + 646 = 143412
Step 223: 143412 + 646 = 144058
Step 224: 144058 + 646 = 144704
Step 225: 144704 + 646 = 145350
Step 226: 145350 + 646 = 145996
Step 227: 145996 + 646 = 146642
Step 228: 146642 + 646 = 147288
Step 229: 147288 + 646 = 147934
Step 230: 147934 + 646 = 148580
Step 231: 148580 + 646 = 149226
Step 232: 149226 + 646 = 149872
Step 233: 149872 + 646 = 150518
Step 234: 150518 + 646 = 151164
Step 235: 151164 + 646 = 151810
Step 236: 151810 + 646 = 152456
Step 237: 152456 + 646 = 153102
Step 238: 153102 + 646 = 153748
Step 239: 153748 + 646 = 154394
Step 240: 154394 + 646 = 155040
Step 241: 155040 + 646 = 155686
Step 242: 155686 + 646 = 156332
Step 243: 156332 + 646 = 156978
Step 244: 156978 + 646 = 157624
Step 245: 157624 + 646 = 158270
Step 246: 158270 + 646 = 158916
Step 247: 158916 + 646 = 159562
Step 248: 159562 + 646 = 160208
Step 249: 160208 + 646 = 160854
Step 250: 160854 + 646 = 161500
Step 251: 161500 + 646 = 162146
Step 252: 162146 + 646 = 162792
Step 253: 162792 + 646 = 163438
Step 254: 163438 + 646 = 164084
Step 255: 164084 + 646 = 164730
Step 256: 164730 + 646 = 165376
Step 257: 165376 + 646 = 166022
Step 258: 166022 + 646 = 166668
Step 259: 166668 + 646 = 167314
Step 260: 167314 + 646 = 167960
Step 261: 167960 + 646 = 168606
Step 262: 168606 + 646 = 169252
Step 263: 169252 + 646 = 169898
Step 264: 169898 + 646 = 170544
Step 265: 170544 + 646 = 171190
Step 266: 171190 + 646 = 171836
Step 267: 171836 + 646 = 172482
Step 268: 172482 + 646 = 173128
Step 269: 173128 + 646 = 173774
Step 270: 173774 + 646 = 174420
Step 271: 174420 + 646 = 175066
Step 272: 175066 + 646 = 175712
Step 273: 175712 + 646 = 176358
Step 274: 176358 + 646 = 177004
Step 275: 177004 + 646 = 177650
Step 276: 177650 + 646 = 178296
Step 277: 178296 + 646 = 178942
Step 278: 178942 + 646 = 179588
Step 279: 179588 + 646 = 180234
Step 280: 180234 + 646 = 180880
Step 281: 180880 + 646 = 181526
Step 282: 181526 + 646 = 182172
Step 283: 182172 + 646 = 182818
Step 284: 182818 + 646 = 183464
Step 285: 183464 + 646 = 184110
Step 286: 184110 + 646 = 184756
Step 287: 184756 + 646 = 185402
Step 288: 185402 + 646 = 186048
Step 289: 186048 + 646 = 186694
Step 290: 186694 + 646 = 187340
Step 291: 187340 + 646 = 187986
Step 292: 187986 + 646 = 188632
Step 293: 188632 + 646 = 189278
Step 294: 189278 + 646 = 189924
Step 295: 189924 + 646 = 190570
Step 296: 190570 + 646 = 191216
Step 297: 191216 + 646 = 191862
Step 298: 191862 + 646 = 192508
Step 299: 192508 + 646 = 193154
Step 300: 193154 + 646 = 193800
Step 301: 193800 + 646 = 194446
Step 302: 194446 + 646 = 195092
Step 303: 195092 + 646 = 195738
Step 304: 195738 + 646 = 196384
Step 305: 196384 + 646 = 197030
Step 306: 197030 + 646 = 197676
Step 307: 197676 + 646 = 198322
Step 308: 198322 + 646 = 198968
Step 309: 198968 + 646 = 199614
Step 310: 199614 + 646 = 200260
Step 311: 200260 + 646 = 200906
Step 312: 200906 + 646 = 201552
Step 313: 201552 + 646 = 202198
Step 314: 202198 + 646 = 202844
Step 315: 202844 + 646 = 203490
Step 316: 203490 + 646 = 204136
Step 317: 204136 + 646 = 204782
Step 318: 204782 + 646 = 205428
Step 319: 205428 + 646 = 206074
Step 320: 206074 + 646 = 206720
Step 321: 206720 + 646 = 207366
Step 322: 207366 + 646 = 208012
Step 323: 208012 + 646 = 208658
Step 324: 208658 + 646 = 209304
Step 325: 209304 + 646 = 209950
Step 326: 209950 + 646 = 210596
Step 327: 210596 + 646 = 211242
Step 328: 211242 + 646 = 211888
Step 329: 211888 + 646 = 212534
Step 330: 212534 + 646 = 213180
Step 331: 213180 + 646 = 213826
Step 332: 213826 + 646 = 214472
Step 333: 214472 + 646 = 215118
Step 334: 215118 + 646 = 215764
Step 335: 215764 + 646 = 216410
Step 336: 216410 + 646 = 217056
Step 337: 217056 + 646 = 217702
Step 338: 217702 + 646 = 218348
Step 339: 218348 + 646 = 218994
Step 340: 218994 + 646 = 219640
Step 341: 219640 + 646 = 220286
Step 342: 220286 + 646 = 220932
Step 343: 220932 + 646 = 221578
Step 344: 221578 + 646 = 222224
Step 345: 222224 + 646 = 222870
Step 346: 222870 + 646 = 223516
Step 347: 223516 + 646 = 224162
Step 348: 224162 + 646 = 224808
Step 349: 224808 + 646 = 225454
Step 350: 225454 + 646 = 226100
Step 351: 226100 + 646 = 226746
Step 352: 226746 + 646 = 227392
Step 353: 227392 + 646 = 228038
Step 354: 228038 + 646 = 228684
Step 355: 228684 + 646 = 229330
Step 356: 229330 + 646 = 229976
Step 357: 229976 + 646 = 230622
Step 358: 230622 + 646 = 231268
Step 359: 231268 + 646 = 231914
Step 360: 231914 + 646 = 232560
Step 361: 232560 + 646 = 233206
Step 362: 233206 + 646 = 233852
Step 363: 233852 + 646 = 234498
Step 364: 234498 + 646 = 235144
Step 365: 235144 + 646 = 235790
Step 366: 235790 + 646 = 236436
Step 367: 236436 + 646 = 237082
Step 368: 237082 + 646 = 237728
Step 369: 237728 + 646 = 238374
Step 370: 238374 + 646 = 239020
Step 371: 239020 + 646 = 239666
Step 372: 239666 + 646 = 240312
Step 373: 240312 + 646 = 240958
Step 374: 240958 + 646 = 241604
Step 375: 241604 + 646 = 242250
Step 376: 242250 + 646 = 242896
Step 377: 242896 + 646 = 243542
Step 378: 243542 + 646 = 244188
Step 379: 244188 + 646 = 244834
Step 380: 244834 + 646 = 245480
Step 381: 245480 + 646 = 246126
Step 382: 246126 + 646 = 246772
Step 383: 246772 + 646 = 247418
Step 384: 247418 + 646 = 248064
Step 385: 248064 + 646 = 248710
Step 386: 248710 + 646 = 249356
Step 387: 249356 + 646 = 250002
Step 388: 250002 + 646 = 250648
Step 389: 250648 + 646 = 251294
Step 390: 251294 + 646 = 251940
Step 391: 251940 + 646 = 252586
Step 392: 252586 + 646 = 253232
Step 393: 253232 + 646 = 253878
Step 394: 253878 + 646 = 254524
Step 395: 254524 + 646 = 255170
Step 396: 255170 + 646 = 255816
Step 397: 255816 + 646 = 256462
Step 398: 256462 + 646 = 257108
Step 399: 257108 + 646 = 257754
Step 400: 257754 + 646 = 258400
Step 401: 258400 + 646 = 259046
Step 402: 259046 + 646 = 259692
Step 403: 259692 + 646 = 260338
Step 404: 260338 + 646 = 260984
Step 405: 260984 + 646 = 261630
Step 406: 261630 + 646 = 262276
Step 407: 262276 + 646 = 262922
Step 408: 262922 + 646 = 263568
Step 409: 263568 + 646 = 264214
Step 410: 264214 + 646 = 264860
Step 411: 264860 + 646 = 265506
Step 412: 265506 + 646 = 266152
Step 413: 266152 + 646 = 266798
Step 414: 266798 + 646 = 267444
Step 415: 267444 + 646 = 268090

So, 646*415 = 268090