text: how many days in total would the food last? many years ago, a cruise liner sank in the middle of the atlantic ocean. the survivors luckily landed on a remote desert island. there was enough food for the 135 people to last four weeks.  nine days later a rescue ship appeared, unluckily this ship also sank, leaving an additional 36 people stranded on the island to now share the original rationed food. the food obviously had to be re-rationed, everyone was now on three-quarters of the original ration, so how many days in total would the food last for, from the day of the original sinking? originally, there was enough to feed 135 people for 28 days, so 135 * 28 = 3,780 daily rations.  after 9 days, there were 135 * 19 = 2,565 daily rations.  now there are 36 additional people, making 135 + 36 = 171 people.  new rations are 3/4 the original size, so there are 4/3 * 2,565 = 3,420 "new rations".  3,420 "new rations" / 171 people = 20 days.  add back the original 9, and the food lasts 29 days.