Question

a fort had provisions for 300 men for 90days.after 20 days,50 men left the fort. how long would the food last at the same rate

Answer 1

After 20 days; 300 men had food for 70 days
suppose 250 boys had food for x days, now less boys more days (indirect proportion)
therefore;
                     250 : 300 :: 70 : x
                     250×x=300×70
                     x=84days..
hope it helps..........
                      

Answer 2

A fort had provisions for 300 men for 90 days. After 20 days, 50 men left the fort. How long would the food last at the same rate.

So men is inversely proportional to days

so with 300 and 90 the constant is 27000

if you use the fact that after 20 days 50 men left you can use 250 men and you get 108 days is that correct
After 20 days, 70 days left and (300*70 = ) 21000 man-days of food left for 250 men.

That will last them (21000/250 =) 84 days.
HOPE IT HELPS YOU