A fort had provision of food for 150 men for 45 days. After 10 days, 25 men left the fort. The number of days for which the remaining food will last, is:

After 10 days : 150 men had food for 35 days.
Suppose 125 men had food for x days.
Now, Less men, More days (Indirect Proportion)
$$\eqalign{ & \therefore 125:150::35:x \cr & \Rightarrow 125 \times x = 150 \times 35 \cr & \Rightarrow x = \frac{{150 \times 35}}{{125}} \cr & \Rightarrow x = 42 \cr} $$