Well first of all if I had a multiplication question such as 12,000×1000 of course you would know it would be 12,000 well you would always use your place value chart saying ones tens hundreds thousands and thousands and hundreds
If you had a problem like 80x20 you wouldn't know what that was but you can take out the 0's and do 8x2 which is 16 then add back both 0's to make 1,600
