50 people consume 350 kg of rice in 30 days. In how many days will 35 people consume 50 kg of rice ?

Let the required number of days be x
Less people, More days (Indirect proportion)
Less quantity, Less days ( Direct proportion)
\[\left. \begin{gathered} \,\,\,\,\,\,\,{\text{People 35}}:50 \hfill \\ {\text{Quantity 350}}:50 \hfill \\ \end{gathered} \right\}::30:x\]
$$\eqalign{ & \therefore {\text{ }}35 \times 350 \times x = 50 \times 50 \times 30 \cr & \Leftrightarrow x = \frac{{\left( {50 \times 50 \times 30} \right)}}{{\left( {35 \times 350} \right)}} \cr & \Leftrightarrow x = \frac{{300}}{{49}} \cr & \Leftrightarrow x = 6\frac{6}{{49}} \cr} $$