Without delay, let's solve this. We've got 421 and we will be multiplying it by 16, that is, adding 421 to itself 16 times.
Step 1: 0 + 421 = 421
Step 2: 421 + 421 = 842
Step 3: 842 + 421 = 1263
Step 4: 1263 + 421 = 1684
Step 5: 1684 + 421 = 2105
Step 6: 2105 + 421 = 2526
Step 7: 2526 + 421 = 2947
Step 8: 2947 + 421 = 3368
Step 9: 3368 + 421 = 3789
Step 10: 3789 + 421 = 4210
Step 11: 4210 + 421 = 4631
Step 12: 4631 + 421 = 5052
Step 13: 5052 + 421 = 5473
Step 14: 5473 + 421 = 5894
Step 15: 5894 + 421 = 6315
Step 16: 6315 + 421 = 6736

So, 421*16 = 6736