a "whole" will be 7/7, or just 1 whole.
so we know one bag can do 1/7 of all students, how many will it be needed to do 7/7?
well, in 7/7 there are seven 7/7, so, 7 bags then, or one could say,
[tex]\bf \begin{array}{ccll}
\stackrel{chocolate}{bag}&\stackrel{fraction}{students}\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
1&\frac{1}{7}\\\\
x&\frac{7}{7}
\end{array}\implies \cfrac{1}{x}=\cfrac{\quad \frac{1}{7}\quad }{\frac{7}{7}}\implies \cfrac{1}{x}=\cfrac{1}{7}\cdot \cfrac{7}{7}
\\\\\\
\cfrac{1}{x}=\cfrac{1}{7}\implies 7=x[/tex]
