Koperta na listy waży  $\frac{2}{5}$  dag.

a) 2 koperty

$\frac{2}{5}\text{dag}+\frac{2}{5}\text{dag}=\frac{4}{5}\text{dag}$   

2 koperty ważą  $\frac{4}{5}$  dag.

 

b) 5 kopert

$\frac{2}{5}\text{dag}+\frac{2}{5}\text{dag}+\frac{2}{5}\text{dag}+\frac{2}{5}\text{dag}+\frac{2}{5}\text{dag}=\frac{10}{5}\text{dag}=2\text{dag}$  

5 kopert waży 2 dag.

 

c) 7 kopert

$\frac{2}{5}\text{dag}+\frac{2}{5}\text{dag}+\frac{2}{5}\text{dag}+\frac{2}{5}\text{dag}+\frac{2}{5}\text{dag}+\frac{2}{5}\text{dag}+\frac{2}{5}\text{dag}=\frac{14}{5}\text{dag}=2\frac{4}{5}\text{dag}$  

7 kopert waży  $2\frac{4}{5}$  dag.