question_answer 1)

                A farmer has enough food to feed 20 animals in his cattle for 6 days. How long would the food last if there were 10 more animals in his cattle?

Answer:

                Suppose that the food would last for \[x\] days. We have the following table.

Number of animals	20	\[20+10=30\]
Number of days	6	\[x\]

We note that more the number of animals, lesser will be the number of days for which the food will last. Therefore, this is a case of inverse proportion. So,          \[20\times 6=30\times x\] \[\Rightarrow \]               \[x=\frac{20\times 6}{30}\] \[\Rightarrow \]               \[x=4\]                 Hence, the food would last for 4 days.