OK, let's work through this together. We're starting with 243 and we're going to multiply it by 324, which means we add 243 to itself 324 times.
Step 1: 0 + 243 = 243
Step 2: 243 + 243 = 486
Step 3: 486 + 243 = 729
Step 4: 729 + 243 = 972
Step 5: 972 + 243 = 1215
Step 6: 1215 + 243 = 1458
Step 7: 1458 + 243 = 1701
Step 8: 1701 + 243 = 1944
Step 9: 1944 + 243 = 2187
Step 10: 2187 + 243 = 2430
Step 11: 2430 + 243 = 2673
Step 12: 2673 + 243 = 2916
Step 13: 2916 + 243 = 3159
Step 14: 3159 + 243 = 3402
Step 15: 3402 + 243 = 3645
Step 16: 3645 + 243 = 3888
Step 17: 3888 + 243 = 4131
Step 18: 4131 + 243 = 4374
Step 19: 4374 + 243 = 4617
Step 20: 4617 + 243 = 4860
Step 21: 4860 + 243 = 5103
Step 22: 5103 + 243 = 5346
Step 23: 5346 + 243 = 5589
Step 24: 5589 + 243 = 5832
Step 25: 5832 + 243 = 6075
Step 26: 6075 + 243 = 6318
Step 27: 6318 + 243 = 6561
Step 28: 6561 + 243 = 6804
Step 29: 6804 + 243 = 7047
Step 30: 7047 + 243 = 7290
Step 31: 7290 + 243 = 7533
Step 32: 7533 + 243 = 7776
Step 33: 7776 + 243 = 8019
Step 34: 8019 + 243 = 8262
Step 35: 8262 + 243 = 8505
Step 36: 8505 + 243 = 8748
Step 37: 8748 + 243 = 8991
Step 38: 8991 + 243 = 9234
Step 39: 9234 + 243 = 9477
Step 40: 9477 + 243 = 9720
Step 41: 9720 + 243 = 9963
Step 42: 9963 + 243 = 10206
Step 43: 10206 + 243 = 10449
Step 44: 10449 + 243 = 10692
Step 45: 10692 + 243 = 10935
Step 46: 10935 + 243 = 11178
Step 47: 11178 + 243 = 11421
Step 48: 11421 + 243 = 11664
Step 49: 11664 + 243 = 11907
Step 50: 11907 + 243 = 12150
Step 51: 12150 + 243 = 12393
Step 52: 12393 + 243 = 12636
Step 53: 12636 + 243 = 12879
Step 54: 12879 + 243 = 13122
Step 55: 13122 + 243 = 13365
Step 56: 13365 + 243 = 13608
Step 57: 13608 + 243 = 13851
Step 58: 13851 + 243 = 14094
Step 59: 14094 + 243 = 14337
Step 60: 14337 + 243 = 14580
Step 61: 14580 + 243 = 14823
Step 62: 14823 + 243 = 15066
Step 63: 15066 + 243 = 15309
Step 64: 15309 + 243 = 15552
Step 65: 15552 + 243 = 15795
Step 66: 15795 + 243 = 16038
Step 67: 16038 + 243 = 16281
Step 68: 16281 + 243 = 16524
Step 69: 16524 + 243 = 16767
Step 70: 16767 + 243 = 17010
Step 71: 17010 + 243 = 17253
Step 72: 17253 + 243 = 17496
Step 73: 17496 + 243 = 17739
Step 74: 17739 + 243 = 17982
Step 75: 17982 + 243 = 18225
Step 76: 18225 + 243 = 18468
Step 77: 18468 + 243 = 18711
Step 78: 18711 + 243 = 18954
Step 79: 18954 + 243 = 19197
Step 80: 19197 + 243 = 19440
Step 81: 19440 + 243 = 19683
Step 82: 19683 + 243 = 19926
Step 83: 19926 + 243 = 20169
Step 84: 20169 + 243 = 20412
Step 85: 20412 + 243 = 20655
Step 86: 20655 + 243 = 20898
Step 87: 20898 + 243 = 21141
Step 88: 21141 + 243 = 21384
Step 89: 21384 + 243 = 21627
Step 90: 21627 + 243 = 21870
Step 91: 21870 + 243 = 22113
Step 92: 22113 + 243 = 22356
Step 93: 22356 + 243 = 22599
Step 94: 22599 + 243 = 22842
Step 95: 22842 + 243 = 23085
Step 96: 23085 + 243 = 23328
Step 97: 23328 + 243 = 23571
Step 98: 23571 + 243 = 23814
Step 99: 23814 + 243 = 24057
Step 100: 24057 + 243 = 24300
Step 101: 24300 + 243 = 24543
Step 102: 24543 + 243 = 24786
Step 103: 24786 + 243 = 25029
Step 104: 25029 + 243 = 25272
Step 105: 25272 + 243 = 25515
Step 106: 25515 + 243 = 25758
Step 107: 25758 + 243 = 26001
Step 108: 26001 + 243 = 26244
Step 109: 26244 + 243 = 26487
Step 110: 26487 + 243 = 26730
Step 111: 26730 + 243 = 26973
Step 112: 26973 + 243 = 27216
Step 113: 27216 + 243 = 27459
Step 114: 27459 + 243 = 27702
Step 115: 27702 + 243 = 27945
Step 116: 27945 + 243 = 28188
Step 117: 28188 + 243 = 28431
Step 118: 28431 + 243 = 28674
Step 119: 28674 + 243 = 28917
Step 120: 28917 + 243 = 29160
Step 121: 29160 + 243 = 29403
Step 122: 29403 + 243 = 29646
Step 123: 29646 + 243 = 29889
Step 124: 29889 + 243 = 30132
Step 125: 30132 + 243 = 30375
Step 126: 30375 + 243 = 30618
Step 127: 30618 + 243 = 30861
Step 128: 30861 + 243 = 31104
Step 129: 31104 + 243 = 31347
Step 130: 31347 + 243 = 31590
Step 131: 31590 + 243 = 31833
Step 132: 31833 + 243 = 32076
Step 133: 32076 + 243 = 32319
Step 134: 32319 + 243 = 32562
Step 135: 32562 + 243 = 32805
Step 136: 32805 + 243 = 33048
Step 137: 33048 + 243 = 33291
Step 138: 33291 + 243 = 33534
Step 139: 33534 + 243 = 33777
Step 140: 33777 + 243 = 34020
Step 141: 34020 + 243 = 34263
Step 142: 34263 + 243 = 34506
Step 143: 34506 + 243 = 34749
Step 144: 34749 + 243 = 34992
Step 145: 34992 + 243 = 35235
Step 146: 35235 + 243 = 35478
Step 147: 35478 + 243 = 35721
Step 148: 35721 + 243 = 35964
Step 149: 35964 + 243 = 36207
Step 150: 36207 + 243 = 36450
Step 151: 36450 + 243 = 36693
Step 152: 36693 + 243 = 36936
Step 153: 36936 + 243 = 37179
Step 154: 37179 + 243 = 37422
Step 155: 37422 + 243 = 37665
Step 156: 37665 + 243 = 37908
Step 157: 37908 + 243 = 38151
Step 158: 38151 + 243 = 38394
Step 159: 38394 + 243 = 38637
Step 160: 38637 + 243 = 38880
Step 161: 38880 + 243 = 39123
Step 162: 39123 + 243 = 39366
Step 163: 39366 + 243 = 39609
Step 164: 39609 + 243 = 39852
Step 165: 39852 + 243 = 40095
Step 166: 40095 + 243 = 40338
Step 167: 40338 + 243 = 40581
Step 168: 40581 + 243 = 40824
Step 169: 40824 + 243 = 41067
Step 170: 41067 + 243 = 41310
Step 171: 41310 + 243 = 41553
Step 172: 41553 + 243 = 41796
Step 173: 41796 + 243 = 42039
Step 174: 42039 + 243 = 42282
Step 175: 42282 + 243 = 42525
Step 176: 42525 + 243 = 42768
Step 177: 42768 + 243 = 43011
Step 178: 43011 + 243 = 43254
Step 179: 43254 + 243 = 43497
Step 180: 43497 + 243 = 43740
Step 181: 43740 + 243 = 43983
Step 182: 43983 + 243 = 44226
Step 183: 44226 + 243 = 44469
Step 184: 44469 + 243 = 44712
Step 185: 44712 + 243 = 44955
Step 186: 44955 + 243 = 45198
Step 187: 45198 + 243 = 45441
Step 188: 45441 + 243 = 45684
Step 189: 45684 + 243 = 45927
Step 190: 45927 + 243 = 46170
Step 191: 46170 + 243 = 46413
Step 192: 46413 + 243 = 46656
Step 193: 46656 + 243 = 46899
Step 194: 46899 + 243 = 47142
Step 195: 47142 + 243 = 47385
Step 196: 47385 + 243 = 47628
Step 197: 47628 + 243 = 47871
Step 198: 47871 + 243 = 48114
Step 199: 48114 + 243 = 48357
Step 200: 48357 + 243 = 48600
Step 201: 48600 + 243 = 48843
Step 202: 48843 + 243 = 49086
Step 203: 49086 + 243 = 49329
Step 204: 49329 + 243 = 49572
Step 205: 49572 + 243 = 49815
Step 206: 49815 + 243 = 50058
Step 207: 50058 + 243 = 50301
Step 208: 50301 + 243 = 50544
Step 209: 50544 + 243 = 50787
Step 210: 50787 + 243 = 51030
Step 211: 51030 + 243 = 51273
Step 212: 51273 + 243 = 51516
Step 213: 51516 + 243 = 51759
Step 214: 51759 + 243 = 52002
Step 215: 52002 + 243 = 52245
Step 216: 52245 + 243 = 52488
Step 217: 52488 + 243 = 52731
Step 218: 52731 + 243 = 52974
Step 219: 52974 + 243 = 53217
Step 220: 53217 + 243 = 53460
Step 221: 53460 + 243 = 53703
Step 222: 53703 + 243 = 53946
Step 223: 53946 + 243 = 54189
Step 224: 54189 + 243 = 54432
Step 225: 54432 + 243 = 54675
Step 226: 54675 + 243 = 54918
Step 227: 54918 + 243 = 55161
Step 228: 55161 + 243 = 55404
Step 229: 55404 + 243 = 55647
Step 230: 55647 + 243 = 55890
Step 231: 55890 + 243 = 56133
Step 232: 56133 + 243 = 56376
Step 233: 56376 + 243 = 56619
Step 234: 56619 + 243 = 56862
Step 235: 56862 + 243 = 57105
Step 236: 57105 + 243 = 57348
Step 237: 57348 + 243 = 57591
Step 238: 57591 + 243 = 57834
Step 239: 57834 + 243 = 58077
Step 240: 58077 + 243 = 58320
Step 241: 58320 + 243 = 58563
Step 242: 58563 + 243 = 58806
Step 243: 58806 + 243 = 59049
Step 244: 59049 + 243 = 59292
Step 245: 59292 + 243 = 59535
Step 246: 59535 + 243 = 59778
Step 247: 59778 + 243 = 60021
Step 248: 60021 + 243 = 60264
Step 249: 60264 + 243 = 60507
Step 250: 60507 + 243 = 60750
Step 251: 60750 + 243 = 60993
Step 252: 60993 + 243 = 61236
Step 253: 61236 + 243 = 61479
Step 254: 61479 + 243 = 61722
Step 255: 61722 + 243 = 61965
Step 256: 61965 + 243 = 62208
Step 257: 62208 + 243 = 62451
Step 258: 62451 + 243 = 62694
Step 259: 62694 + 243 = 62937
Step 260: 62937 + 243 = 63180
Step 261: 63180 + 243 = 63423
Step 262: 63423 + 243 = 63666
Step 263: 63666 + 243 = 63909
Step 264: 63909 + 243 = 64152
Step 265: 64152 + 243 = 64395
Step 266: 64395 + 243 = 64638
Step 267: 64638 + 243 = 64881
Step 268: 64881 + 243 = 65124
Step 269: 65124 + 243 = 65367
Step 270: 65367 + 243 = 65610
Step 271: 65610 + 243 = 65853
Step 272: 65853 + 243 = 66096
Step 273: 66096 + 243 = 66339
Step 274: 66339 + 243 = 66582
Step 275: 66582 + 243 = 66825
Step 276: 66825 + 243 = 67068
Step 277: 67068 + 243 = 67311
Step 278: 67311 + 243 = 67554
Step 279: 67554 + 243 = 67797
Step 280: 67797 + 243 = 68040
Step 281: 68040 + 243 = 68283
Step 282: 68283 + 243 = 68526
Step 283: 68526 + 243 = 68769
Step 284: 68769 + 243 = 69012
Step 285: 69012 + 243 = 69255
Step 286: 69255 + 243 = 69498
Step 287: 69498 + 243 = 69741
Step 288: 69741 + 243 = 69984
Step 289: 69984 + 243 = 70227
Step 290: 70227 + 243 = 70470
Step 291: 70470 + 243 = 70713
Step 292: 70713 + 243 = 70956
Step 293: 70956 + 243 = 71199
Step 294: 71199 + 243 = 71442
Step 295: 71442 + 243 = 71685
Step 296: 71685 + 243 = 71928
Step 297: 71928 + 243 = 72171
Step 298: 72171 + 243 = 72414
Step 299: 72414 + 243 = 72657
Step 300: 72657 + 243 = 72900
Step 301: 72900 + 243 = 73143
Step 302: 73143 + 243 = 73386
Step 303: 73386 + 243 = 73629
Step 304: 73629 + 243 = 73872
Step 305: 73872 + 243 = 74115
Step 306: 74115 + 243 = 74358
Step 307: 74358 + 243 = 74601
Step 308: 74601 + 243 = 74844
Step 309: 74844 + 243 = 75087
Step 310: 75087 + 243 = 75330
Step 311: 75330 + 243 = 75573
Step 312: 75573 + 243 = 75816
Step 313: 75816 + 243 = 76059
Step 314: 76059 + 243 = 76302
Step 315: 76302 + 243 = 76545
Step 316: 76545 + 243 = 76788
Step 317: 76788 + 243 = 77031
Step 318: 77031 + 243 = 77274
Step 319: 77274 + 243 = 77517
Step 320: 77517 + 243 = 77760
Step 321: 77760 + 243 = 78003
Step 322: 78003 + 243 = 78246
Step 323: 78246 + 243 = 78489
Step 324: 78489 + 243 = 78732

So, 243*324 = 78732