Let's get this math done. We have 210 and we're going to multiply it by 81. This is the same as taking 210 and adding it to itself 81 times.
Step 1: 0 + 210 = 210
Step 2: 210 + 210 = 420
Step 3: 420 + 210 = 630
Step 4: 630 + 210 = 840
Step 5: 840 + 210 = 1050
Step 6: 1050 + 210 = 1260
Step 7: 1260 + 210 = 1470
Step 8: 1470 + 210 = 1680
Step 9: 1680 + 210 = 1890
Step 10: 1890 + 210 = 2100
Step 11: 2100 + 210 = 2310
Step 12: 2310 + 210 = 2520
Step 13: 2520 + 210 = 2730
Step 14: 2730 + 210 = 2940
Step 15: 2940 + 210 = 3150
Step 16: 3150 + 210 = 3360
Step 17: 3360 + 210 = 3570
Step 18: 3570 + 210 = 3780
Step 19: 3780 + 210 = 3990
Step 20: 3990 + 210 = 4200
Step 21: 4200 + 210 = 4410
Step 22: 4410 + 210 = 4620
Step 23: 4620 + 210 = 4830
Step 24: 4830 + 210 = 5040
Step 25: 5040 + 210 = 5250
Step 26: 5250 + 210 = 5460
Step 27: 5460 + 210 = 5670
Step 28: 5670 + 210 = 5880
Step 29: 5880 + 210 = 6090
Step 30: 6090 + 210 = 6300
Step 31: 6300 + 210 = 6510
Step 32: 6510 + 210 = 6720
Step 33: 6720 + 210 = 6930
Step 34: 6930 + 210 = 7140
Step 35: 7140 + 210 = 7350
Step 36: 7350 + 210 = 7560
Step 37: 7560 + 210 = 7770
Step 38: 7770 + 210 = 7980
Step 39: 7980 + 210 = 8190
Step 40: 8190 + 210 = 8400
Step 41: 8400 + 210 = 8610
Step 42: 8610 + 210 = 8820
Step 43: 8820 + 210 = 9030
Step 44: 9030 + 210 = 9240
Step 45: 9240 + 210 = 9450
Step 46: 9450 + 210 = 9660
Step 47: 9660 + 210 = 9870
Step 48: 9870 + 210 = 10080
Step 49: 10080 + 210 = 10290
Step 50: 10290 + 210 = 10500
Step 51: 10500 + 210 = 10710
Step 52: 10710 + 210 = 10920
Step 53: 10920 + 210 = 11130
Step 54: 11130 + 210 = 11340
Step 55: 11340 + 210 = 11550
Step 56: 11550 + 210 = 11760
Step 57: 11760 + 210 = 11970
Step 58: 11970 + 210 = 12180
Step 59: 12180 + 210 = 12390
Step 60: 12390 + 210 = 12600
Step 61: 12600 + 210 = 12810
Step 62: 12810 + 210 = 13020
Step 63: 13020 + 210 = 13230
Step 64: 13230 + 210 = 13440
Step 65: 13440 + 210 = 13650
Step 66: 13650 + 210 = 13860
Step 67: 13860 + 210 = 14070
Step 68: 14070 + 210 = 14280
Step 69: 14280 + 210 = 14490
Step 70: 14490 + 210 = 14700
Step 71: 14700 + 210 = 14910
Step 72: 14910 + 210 = 15120
Step 73: 15120 + 210 = 15330
Step 74: 15330 + 210 = 15540
Step 75: 15540 + 210 = 15750
Step 76: 15750 + 210 = 15960
Step 77: 15960 + 210 = 16170
Step 78: 16170 + 210 = 16380
Step 79: 16380 + 210 = 16590
Step 80: 16590 + 210 = 16800
Step 81: 16800 + 210 = 17010

So, 210*81 = 17010