Even if you’re not an engineer or mathematician, you’ll surely find uses for these simple tricks. So take a look and be ready to impress people with your computational skills!
It’s a little trickier, but you can learn about that one here.
The question is “What’s 32 x 31?”
You draw the lines out as shown, then count the intersections of lines in each area. Read the results backwards and…that’s it. You’re a genius!