Let the number of days that the food will last if there were 10 more animals in the cattle be x. The following table is obtained.

Number of animals | 20 | 20 + 10 = 30 |

Number of days | 6 | x |

More the number of animals, lesser will be the number of days for which the food will last.

Hence, the number of days the food will last and the number of animals are inversely

proportional to each other.

Therefore,

20 × 6 = 30 × x

x = (20 x6)/30 = 4

Thus, the food will last for 4 days.