• # question_answer 15)                 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?

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.