Question

Determinati numarul natural de forma ab,scris in baza 10, stiind ca ab supra ba= 2 supra 9.

Answer 1

$\frac{ab}{ba}= \frac{2}{9}=>2*ba=9ab<=> \\ \\ <=>2(10b+a)=9(10a+b)<=> \\ \\ <=>20b+2a=90a+9b<=> \\ \\ <=> 11b=88a=>b=8a=>b=8~si~a=1. \\ \\ Soltuie~ab=18.$