5 cool math tricks ft. Technicality

I never did that finger thing with the 9s. I was actually taught an easier method, imo. 

Take any 9 times table under 1-10. Let's say 9 * 4.

Take the 4, subtract 1. You get 3. 
Now subtract 3 from 9. You get 6. 
Answer is 36. 

Or, if you're more inclined, you can use your fingers (or count in your head if you prefer)
4 - 1 = 3. Then count the numbers from 3 to 9, you get 6. 36. 

You can do this for any 9 times table, not just the ones 1-10. But it gets over complicated. The catch is that every time you enter a new set of 10, you have to multiply the trick one more time. So, for 1-10, you just subtract 1 and use 9. For 11-20, you subtract 2 and use 18 (9 * 2). For 21-30, you subtract 3 and use 27 (9 * 3), etc. 

Say 9 * 18.

Take 18, subtract 2. You get 16.
Take 9 * 2 (18), then subtract 16. You get 2. 
16 and 2: 162. 

Or lets say 9 * 22.
Take 22, subtract 3. You get 19.
Take 9 * 3 (27), then subtract 19. You get 8.
19 and 8: 198.

Or lets say 9 * 35.
Take 35, subtract 4. You get 31.
Take 9 * 4 (36), then subtract 31. You get 5.
31 and 5: 315. 

Or, take 9 * 40.
Take 40, subtract 5. You get 35.
Take 9 * 5 (45), then subtract 35. You get 10.
35 and 10: 360