A farmer has enough food to feed 20 cattle for 6 days. The number of days food will last if there were 10 more cattle is
As the number of animals increases, the number of days the food lasts decreases. They are in inverse proportion.
Let the required number of days be 't'
20 × 6 = 30 × t
t = 4 days
So, the food will last for 4 days.