Question

A FORT HAD ENOUGH FOOD FOR 80 SOLDIER FOR 60 DAYS.HOW LONG WOULD THE FOOD LAST IF 20 MORE SOLDIERS JOIN AFTER 15 DAYS

Answer 1

Solution:-

Total period = 60 days
After 15 days this period will be  = 60 - 15
= 45 days
Number of soldiers in the beginning = 80
Number of soldiers join = 20 
New number of soldiers = 80 + 20 
= 100 Soldiers.
Number of Soldiers                   Days
            80                                   45
          100                                    x 
More men, the food will last lesser days.
This is an inverse proportion.
80 : 100 : : 45 : x
x = (80*45)/100
x = 36 days
15 days has already gone, so, the food will last for 15 + 36 = 51 days instead of 60 days.
Answer.

Answer 2

60 -15=45
45 *80/100=36