is there a trick how to calculate 17x40 faster?

17x40

Double 17=34

Double 34=68

Add a zero = 680

 

That is how I would do it :)

17 x 40 You can try this:

10 x 40 =400

7 x 40 =280

400 + 280 =680

Another possibility:

 

17*40  →  (10 + 7)*4*10  →  (10*4 + 7*4)*10  →  (40 + 28)*10  →  68*10  →  680