11 Plus Exams Forum

A lifeboat has enough drinking water to last a crew of 24 men for 12 days at a half litre per day for each man. They rescue 24 men from the sea. How long will the water now last if the skipper decides to cut the ration to one third of a litre per day.

My DD solved the problem by calculating that there were 48 men on the boat(24 crew+24 rescued men). Are there 24 or 48 men?

Help appreciated. Thanks

Apu1923 wrote:A lifeboat has enough drinking water to last a crew of 24 men for 12 days at a half litre per day for each man. They rescue 24 men from the sea. How long will the water now last if the skipper decides to cut the ration to one third of a litre per day.

My DD solved the problem by calculating that there were 48 men on the boat(24 crew+24 rescued men). Are there 24 or 48 men?

How much water is there: 24 x 12 x 0.5 = 144 litres
There are now 48 men (crew of 24 + 24 rescued)
1/3 of a litre each is 16 litres / day
144 / 16 = 9 days

Thanks Okanagan.

Hi Apu1923! A slightly different approach:

Water available before before the rescue: will last for 24 men for 12 days at ½ litre per day.

Same amount of water available after the rescue: will last for 48 men for D days at 1/3 litre per day.

i.e. 24 x 12 x ½ = 48 x D x 1/3.

So, 144 = 16 x D.

So, D = 144/16 = 9 days.