Question

O carte de povesti are 135 de pagini. De câte ori apare cifra 9 in numerotarea paginilor?
VA ROGGGG AM NEVOIE URGENT!!!!!! PT MAINE​

Answer 1

Răspuns:

135:9=15 ori

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Answer 2

$\it \begin{cases} 9\\19\\29\\39\\49\\59\\69\\79\\89\end{cases}\Rightarrow de\ 9\ ori\\ \\ \\\begin{cases} 90\\91\\92\\93\\94\\95\\96\\97\\98\\99\end{cases} \Rightarrow de\ 11\ ori\\ \\ \\\begin{cases}109\\119\\129\\\end{cases} \Rightarrow de\ 3\ ori\\ \\ \\ Total:\ \ de\ 23\ de\ ori$