Let's roll up our sleeves and solve this. We have 905 and we're going to multiply it by 43, essentially adding 905 to itself 43 times.
Step 1: 0 + 905 = 905
Step 2: 905 + 905 = 1810
Step 3: 1810 + 905 = 2715
Step 4: 2715 + 905 = 3620
Step 5: 3620 + 905 = 4525
Step 6: 4525 + 905 = 5430
Step 7: 5430 + 905 = 6335
Step 8: 6335 + 905 = 7240
Step 9: 7240 + 905 = 8145
Step 10: 8145 + 905 = 9050
Step 11: 9050 + 905 = 9955
Step 12: 9955 + 905 = 10860
Step 13: 10860 + 905 = 11765
Step 14: 11765 + 905 = 12670
Step 15: 12670 + 905 = 13575
Step 16: 13575 + 905 = 14480
Step 17: 14480 + 905 = 15385
Step 18: 15385 + 905 = 16290
Step 19: 16290 + 905 = 17195
Step 20: 17195 + 905 = 18100
Step 21: 18100 + 905 = 19005
Step 22: 19005 + 905 = 19910
Step 23: 19910 + 905 = 20815
Step 24: 20815 + 905 = 21720
Step 25: 21720 + 905 = 22625
Step 26: 22625 + 905 = 23530
Step 27: 23530 + 905 = 24435
Step 28: 24435 + 905 = 25340
Step 29: 25340 + 905 = 26245
Step 30: 26245 + 905 = 27150
Step 31: 27150 + 905 = 28055
Step 32: 28055 + 905 = 28960
Step 33: 28960 + 905 = 29865
Step 34: 29865 + 905 = 30770
Step 35: 30770 + 905 = 31675
Step 36: 31675 + 905 = 32580
Step 37: 32580 + 905 = 33485
Step 38: 33485 + 905 = 34390
Step 39: 34390 + 905 = 35295
Step 40: 35295 + 905 = 36200
Step 41: 36200 + 905 = 37105
Step 42: 37105 + 905 = 38010
Step 43: 38010 + 905 = 38915

So, 905*43 = 38915