Question 1031265
 In a ship there were stored food for 50 sailors for 16 days.
 After 10 days 10 more soldiers joined them.
 How many days the remaining food last?
:
Find how many man-days of food available?
50*16 = 800 man-days of food
:
let d = remaining days of food available, with the additional men added
50(d+10) + 10d = 800
50d + 500 + 10d = 800
50d + 10d = 800 - 500
60d = 300
d = 300/60
d = 5 days
:
:
Check this
Original group consumed 50(10+5) = 750 man-days of food
Additional 10 men consumed:10 * 5 = 50 man-days 
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Total consumption altogether: 800 man-days