Question

Determinati cifra a stiind ca 16,8(a) cu bara de asupra < $\frac{423}{25}$

Answer 1

$\overline{16,8(a)}= \frac{\overline{168a}-168}{90}= \frac{1680+a-168}{90}= \frac{1512+a}{90} . \\ \\ Deci~ \frac{1512+a}{90}\ \textless \ \frac{423}{25}~~~~~~~~~~~~| \cdot 450 \\ \\ 5(1512+a)\ \textless \ 18 \cdot 423 \\ \\ 7560+5a\ \textless \ 7614 \\ \\ 5a\ \textless \ 7614-7560 \\ \\ 5a\ \textless \ 54 ,~a-cifra~\Rightarrow \boxed{a \in \{0,1,2,3,4,5,6,7,8,9\}}~.$

Answer 2

16,8[a]<16,92;
⇒16=16;
⇒8[a]<92⇒a-cifra naturala;
⇒a∈[1,2,3,4,5,6,7,8,9]⇒9 variante de raspuns;