If you had to multiply 101 by 32, you probably already know it would be a hassle to write 101 on top of 32 then keep factoring it out on paper. If you can already multiply 100 out, you can quickly do 101 by 30 in your head to get 3,030 then write 3030 down then multiply 101 times 2 in your head to get 202 then write down 202 then add the two numbers to come up with 3,032 for the answer.