23×2= (20+3)×2= 20 ×2+3×2 =400+6=406
230×2= (200 +30)×2 = 200×2 +30×2 =400 +60 = 460
19×5= (10 +9)×5 = 10×5 + 9×5=50+45=95
23×2= (20+3)×2= 20 ×2+3×2 =400+6=406
230×2= (200 +30)×2 = 200×2 +30×2 =400 +60 = 460
19×5= (10 +9)×5 = 10×5 + 9×5=50+45=95