Question

A bag of chocolate mix weighed 1/4 of a kilogram could make enough brownies to feed 1/7 of the students at school how many bags would be needed to feet all the students?

Answer 1

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,

$\bf \begin{array}{ccll} \stackrel{chocolate}{bag}&\stackrel{fraction}{students}\\ \text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\ 1&\frac{1}{7}\\\\ x&\frac{7}{7} \end{array}\implies \cfrac{1}{x}=\cfrac{\quad \frac{1}{7}\quad }{\frac{7}{7}}\implies \cfrac{1}{x}=\cfrac{1}{7}\cdot \cfrac{7}{7} \\\\\\ \cfrac{1}{x}=\cfrac{1}{7}\implies 7=x$