Let's get this math done. We have 81 and we're going to multiply it by 16. This is the same as taking 81 and adding it to itself 16 times.
Step 1: 0 + 81 = 81
Step 2: 81 + 81 = 162
Step 3: 162 + 81 = 243
Step 4: 243 + 81 = 324
Step 5: 324 + 81 = 405
Step 6: 405 + 81 = 486
Step 7: 486 + 81 = 567
Step 8: 567 + 81 = 648
Step 9: 648 + 81 = 729
Step 10: 729 + 81 = 810
Step 11: 810 + 81 = 891
Step 12: 891 + 81 = 972
Step 13: 972 + 81 = 1053
Step 14: 1053 + 81 = 1134
Step 15: 1134 + 81 = 1215
Step 16: 1215 + 81 = 1296

So, 81*16 = 1296