Let's get this math done. We have 672 and we're going to multiply it by 64. This is the same as taking 672 and adding it to itself 64 times.
Step 1: 0 + 672 = 672
Step 2: 672 + 672 = 1344
Step 3: 1344 + 672 = 2016
Step 4: 2016 + 672 = 2688
Step 5: 2688 + 672 = 3360
Step 6: 3360 + 672 = 4032
Step 7: 4032 + 672 = 4704
Step 8: 4704 + 672 = 5376
Step 9: 5376 + 672 = 6048
Step 10: 6048 + 672 = 6720
Step 11: 6720 + 672 = 7392
Step 12: 7392 + 672 = 8064
Step 13: 8064 + 672 = 8736
Step 14: 8736 + 672 = 9408
Step 15: 9408 + 672 = 10080
Step 16: 10080 + 672 = 10752
Step 17: 10752 + 672 = 11424
Step 18: 11424 + 672 = 12096
Step 19: 12096 + 672 = 12768
Step 20: 12768 + 672 = 13440
Step 21: 13440 + 672 = 14112
Step 22: 14112 + 672 = 14784
Step 23: 14784 + 672 = 15456
Step 24: 15456 + 672 = 16128
Step 25: 16128 + 672 = 16800
Step 26: 16800 + 672 = 17472
Step 27: 17472 + 672 = 18144
Step 28: 18144 + 672 = 18816
Step 29: 18816 + 672 = 19488
Step 30: 19488 + 672 = 20160
Step 31: 20160 + 672 = 20832
Step 32: 20832 + 672 = 21504
Step 33: 21504 + 672 = 22176
Step 34: 22176 + 672 = 22848
Step 35: 22848 + 672 = 23520
Step 36: 23520 + 672 = 24192
Step 37: 24192 + 672 = 24864
Step 38: 24864 + 672 = 25536
Step 39: 25536 + 672 = 26208
Step 40: 26208 + 672 = 26880
Step 41: 26880 + 672 = 27552
Step 42: 27552 + 672 = 28224
Step 43: 28224 + 672 = 28896
Step 44: 28896 + 672 = 29568
Step 45: 29568 + 672 = 30240
Step 46: 30240 + 672 = 30912
Step 47: 30912 + 672 = 31584
Step 48: 31584 + 672 = 32256
Step 49: 32256 + 672 = 32928
Step 50: 32928 + 672 = 33600
Step 51: 33600 + 672 = 34272
Step 52: 34272 + 672 = 34944
Step 53: 34944 + 672 = 35616
Step 54: 35616 + 672 = 36288
Step 55: 36288 + 672 = 36960
Step 56: 36960 + 672 = 37632
Step 57: 37632 + 672 = 38304
Step 58: 38304 + 672 = 38976
Step 59: 38976 + 672 = 39648
Step 60: 39648 + 672 = 40320
Step 61: 40320 + 672 = 40992
Step 62: 40992 + 672 = 41664
Step 63: 41664 + 672 = 42336
Step 64: 42336 + 672 = 43008

So, 672*64 = 43008