How do you calculate 18 x 7 in your head? /u/JCFT_Collins No such thing as stupid questions

I’m interested in hearing how people do relatively simple math in their heads. I’m currently helping my 3rd grader with introduction to multiplication. The teacher requires the students to show their work. They accept a number of different ways to show this, which got me wondering if there is a better way than I currently do it. I realize there are a lot of ways to write it down, but I’m interested in how you do it in your head.

In my head i quickly separate the 8 from the 10. I take 10 x 7 and 8 x 7. I automatically know that to be 70 + 56. And in my head I just automatically know 70 + 56 is 126.

On bigger numbers like 24 x 29, I try to separate into more manageable pairs, but sometimes its not as easy as the sample above.

What do you do?

I’m interested in hearing how people do relatively simple math in their heads. I’m currently helping my 3rd grader with introduction to multiplication. The teacher requires the students to show their work. They accept a number of different ways to show this, which got me wondering if there is a better way than I currently do it. I realize there are a lot of ways to write it down, but I’m interested in how you do it in your head.

In my head i quickly separate the 8 from the 10. I take 10 x 7 and 8 x 7. I automatically know that to be 70 + 56. And in my head I just automatically know 70 + 56 is 126.

On bigger numbers like 24 x 29, I try to separate into more manageable pairs, but sometimes its not as easy as the sample above.

What do you do?