Factorization
By Factoring number,you can break down problems into simpler multiplication tasks.Also,you may be able to apply some techniques you learned.
21*33
step 1 : 21*11*3
Step 2: 231*3
Step 3 :693
67*81
Step 1: 67*9*9
Step 2:603*9=5427
28*125=3500
Step 1: 28*125
Step 2: 28*25*5
Step 3:2 8*(100/4)*5
Step 4:28/4*100*5
Step 5:7*500=3500