$\frac{1}{7}\approx 0,14$

$\frac{2}{9}\approx 0,22$

Zatem przybliżona wartość sumy:

$0,14+0,22=0,36$

A rzeczywista wartość sumy:

$\frac{1}{7}+\frac{2}{9}=\frac{9}{63}+\frac{14}{63}=\frac{23}{63}$

 

Błąd względny:

$\frac{\left|\frac{23}{63}-0,36\right|}{\frac{23}{63}}=\frac{\left|\frac{23}{63}-\frac{36}{100}\right|}{\frac{23}{63}}=\frac{\left|\frac{2300}{6300}-\frac{2268}{6300}\right|}{\frac{23}{63}}=$

$=\frac{\frac{32}{6300}}{\frac{23}{63}}=\frac{32}{\sout{6300}}\cdot \frac{\sout{63}}{23}=\frac{32}{100}\cdot \frac{1}{23}=\frac{32}{2300}\approx 1,4\%$

Odp.: C