A farmer has enough food to feed 28 animals in his cattle for 9 days. How long would the food last, if there were 8 more animals in his cattle?
More the number of animals, lesser the days to feed them by given food. So, it is an inverse proportion.
Let the required days be x.
⇒ 28 × 9 = 36 × x
⇒ x = 
= 7 days
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