A little simpler trick 109×10+109x9=109² Another one if u want to take out a no. For Example 109 multiplied by a even no. Then 109+109=109×2 109×2+109×2= 109×4 109×4+109×2=109x8 Just like that it will be helpful if u r good at addition or doubling a no. In ur mind itself
The simplest way Only if the axiom of equivalence is applied The difference between 110 and 109 is only 1 So 110×y -109×y =x(Than 109×y many y) x=x-y For example:110×8-109×8 =880-8 =872 109×1=110×1-1=109 109×2=110×2-2=218 109×3=110×3-3=327 109×4=110×4-4=436 109×5=110×5-5=545 109×6=110×6-6=654 109×7=110×7-7=763 109×8=110×8-8=872 109×9=110×9-9=981
109 ×2 = 110×2 -2 = 218 109 × 3 = 110×3-3 = 327 And so one Or... it is like 100 × 2 + 9×2 200 + 18 = 18 I just figured this out before reading your comment by myself... is it similar? Thanks for explaining it in detail btw 😊